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BULLETIN

OF THE

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buratflrji

NATURAL HISTORY,

Urbana, Illinois.

VOLUME V.

Contributions to a Knowledge of the Natural
History of Illinois.

1897-1901.

fcfcW YORfc
ttOTANICAk

Illinois State Laboratory of Natural History,

Urbana, 111.

1902.

CONTENTS.

PA9E.

Article I. — Plankton Studies. [. Methods and Appara-
tus in Use in Plankton Investigations at the
Biological Experiment Station of the University
of Illinois. By C. A. Kopoid (7 Plates.)
March, 1897 1

Article II. — A Contribution to a Knowledge of North
American Fresh- water Cyclopidce. By Ernest
B. Forbes (13 Plates.) September, 1897 27

Article III. — The North American Species ot: Diaptomus.
By Frederick William Schacht. (15 Plates.)
December, 1897 97

Article IV — The North American Centropagidce belong-
ing to the Genera Osphranticum, Limnocalanus,
and Episehura. By Frederick William
Schacht. September, "1898 225

Article V. — Plankton Studies. II. On Pleodorina illi-
noisensis, a New Species from the Plankton of
the Illinois River. By C. A. Kofoid. (12
Plates.) September, 1898 273

Article VI — A List of the Protozoa and Botifera found in
the Illinois River and Adjacent Lakes at Havana,
Illinois. By Adolph Hempel. (5 Figures.) Jan-
uary, 1899 301

Article VII. — First Supplement to the Check-List of the

Coccidce. By T. D. A. Cockerell. February,! 899. 389

Article VIII. — A Statistical Study of the Parasites of the

Unionidce. By H. M. Kelly. May, 1899 399

Article IX — Plankton Studies. III. On Plalydorina, a
New Genus of the Family Volvocidai, from the
Plankton of the Illinois River. By C. A. Ko-
foid (1 Plate.) December, 1899 419

Article X. — Notes on Species of North American Oligo-
chmta. III. List of Species found in Illinois,
and Descriptions of Illinois Tabificidcp, By
Frank Smith. (2 Plates ) March. 1900 ". 441

Article XI — Notes on Species of North American Oligo-
chceta. IV. On a New Lumbriculid Genus from
Florida, with additional Notes on the Nephridial
and Circulatory Systems of Me sopor odrilus asym-
metricus Smith. By Frank Smith. (1 Plate.)
June, 1900 459

Article XII. — The Hirudinea of Illinois. By J. Percy

Moore. (8 Plates.) February, 1901 479

BULLETIN

Illinois 3 tate Laboratory

NATURAL HISTORY,

Urbana, Illinois

VOLUME V.

ARTICLE I.— PLANKTON STUDIES. I. METHODS AND
APPARATUS IN USE IN PLANKTON INVESTIGA-
TIONS AT THE BIOLOGICAL EXPERIMENT STA-
TION OE THE UNIVERSITY OF I ILL NO LS.

By C. A. KOFOID, Ph. D.

Illinois State Laboratory of Natural History,

I'RHANA, ILLINOIS.

1897.

State Laboratory of Natural History

LABORATORY STAFF.

Professor Stephen Alfred Forbes, Ph. D..
Director of State Laboratory and State Entomologist.

Charles Arthur Hart.
Systematic Entomologist and Curator of Collections.

Frank Smith, A. M..
Assistant Zoologist.

Charles Atwood Kofoid, Ph. D..
Superintendent of Biological Station.

Charles Christopher Adams, B. S.
Entomo logica I A ssis tant.

Mary .Jane Snyder.
Secretary.

Henry Clinton Forbes,
Librarian and Business Agent.

Lydia Moore Hart,
Artist.

Article I. — Plankton Studies. I. Methods and Apparatus in
Use in Plankton Investigations at the Biological Experi-
ment Station of the University of Illinois. By C. A. Kofoid.

Less than ten years ago a new field of biological science
was opened by the German investigator Hensen, namely, the
quantitative examination of the " Plankton." This term was
applied to all plants and animals floating free in the water
and incapable by their own efforts of materially changing
their position. Thus adult fish which brave the waves and
stem the current would not be included in the plankton,
while the passive eggs or the helpless fry would fall within
the limits of the definition. Practically, the content of the
term plankton as applied to fresh water is the sum total
of its minute life, both plant and animal.

The scope of our plankton work upon the Illinois River and
its adjacent waters includes a continuous, systematic, and
exhaustive examination of the plant and animal life sus-
pended in the waters of a river system, with a view to deter-
mining its amount and seasonal changes, its local and vertical
distribution, its movement and relation to the current, the
effect upon it of floods and of drouth, of light and of tempera-
ture, the organisms which compose it, their seasonal and
cyclic changes, and their mutual interrelations. Added
interest arises from the fact that this is the first application
of this method of biological investigation to a river system
and its related waters.

It is the purpose of the present paper to describe the
methods and apparatus employed in the plankton work at the
Biological Station at Havana, Illinois, during the years 1894-
1896. Both are, as a rule, the result of mutual conference
of the various members of its staff. During the first
fifteen months of the existence of the Station the plankton
work was in the hands of Professor Frank Smith, and when,
on July 1, 1895, the writer assumed charge of this work at
the Station he found the oblique haul, described on a subse-

2 Illinois Stale Laboratory of Natural History.

quent page, already inaugurated and in successful operation.
It now devolves upon him to prepare for publication a de-
scription of this method, hut the credit for devising it and
putting it in operation belongs to those from whose hands he
received it. The apparatus was used without modification
until August 23, 1895, when the detachable bucket was
added to the net, and in October of the same year the separa-'
able carriage was introduced. In May, 1896, the pumping
method was substituted for the oblique haul in making plank-
ton collections.

Upon the opening of the Station in April, 1894, the exam-
ination of the water by the plankton method was decided
upon, and in the early part of June the first regular collections
were made. The method of plankton collection ordinarily
employed, — as, for example, by Hensen ('87 and '95) in the
Baltic and North Seas and in the Atlantic Ocean, by Apstein
('92 and '96) and Zacharias ('93-'96) in the lakes of northern
Germany, by Eeighard ('94) in Lake St. Clair, and by Ward
('96a) in Lake Michigan, — has been without exception the ver-
tical haul, in which the net is lowered to the bottom of the
body of water and then raised in a vertical line to the surface,
thus filtering a vertical column of water. Difficulties beset
the application of this method to the waters at Havana. In
the first place all the bodies of water examined at the Station
are quite shallow, the majority of the plankton collections
being made in less than three meters of water. The river itself
is the deepest water in the locality, but at its lowest stage
there are only three meters of water in the main channel,
where collections are made. This depth is increased at times
of flood, the maximum reached in the past three years being
6.1 meters. The shallowness of the water thus practically
precludes examination by means of the vertical haul.

A second difficulty exists in the unstable nature of the
bottom generally found throughout the locality to which the
operations of the Station are confined. This consists of a soft
black mud, composed largely of the detritus of decaying veg-
etation and alluvial soil deposited from the silt- charged waters
at times of flood. It is extremely unstable and upon the least

Methods in Plankton Investigations. 3

i> '

disturbance mingles with the water, rendering it impossible to
take a clean plankton collection. The soiling of the net and
the fouling of the water consequent upon dropping a large
plankton net upon the bottom further preclude the vertical
haul in the plankton work at Havana.

I. THE OBLIQUE-HAUL METHOD. (PLATES I.-III.)

The oblique haul was at first adopted as the method best
suited to the situation. This is accomplished by suspend-
ing the net to a carriage which runs upon a rope stretched
obliquely from the bottom to the surface of the water. By
this means the column of water traversed by the net is
increased to an adequate length. It also permits the employ-
ment of a net small enough to be easily operated from a row-
boat. A short description of this method of plankton collection
has been given by Professor Forbes ('94). The parts of the
apparatus used in making the oblique haul will now be de-
scribed.

1. The Quantitative Net (Plates I. and II.). — The net used
by us is the modification of the Hensen net suggested by
Apstein ('91 and '92) for fresh- water work, and more fully
described by him ('96) as the smaller model quantitative net.
It consists of three parts : (a) the filtering net proper, (/>) the
detachable bucket, and (r) the head-piece of the net.

a. The filtering net has the form of an inverted truncated
cone, whose base has a diameter of 25 cm. and whose side is
40 cm. The truncated apex, to which the bucket is attached,
is 4 cm. in outside diameter. This net is made of No. 20
silk bolting cloth, which can be obtained from wholesale
dealers in supplies for flouring mills. That used by us bears
the brand, " Especially for milling purposes. Dufour & Com-
pany." This is the same brand of cloth as that which was
used by Pieighard ('94) and Ward ('96a) in their plankton
work upon the Great Lakes. It is stated by the manufact-
urers to contain 29,929 meshes to the English square inch.
Examination under the microscope shows that this cloth
contains 32477 (— 172.75x188) meshes to the square
inch after sponging and pressing with a hot iron four times.

4 Illinois State Laboratory of Natural History.

The average area of the openings is reported by Reighard
('94, p. 57) to be:

.00003596 sq. cm. in the new cloth,

.00002808 sq. cm. in cloth that had been wetted and then
dried,

.00002336 sq. cm. in cloth that had been used for 40
hauls of a net.

As the new silk shrinks considerably after its first wetting,
we have followed the practice of thoroughly and repeatedly
sponging it and pressing it with a hot iron before cutting out
the net. Otherwise in a single-seam net there is sufficient
shrinkage to cause the filtering cone to take a position oblique
to the true axis of the net (See Apstein, '96, p. 34, Fig. 3).

The following directions for making a pattern for the net
are here inserted, as they may be of use to those to whom the
original descriptions given by Apstein ('91, '92, and '96) are
inaccessible.

GrlRX

Fiq.A

Fif, r , A. — Completed cone. Fig. B.— Completed pattern for the silk net.
(Both after Apstein.)

The net has the form of a truncated cone (Fig. A), whose
side (i = 40 cm.) and radii of the ends (A' 12.5 cm., and
r = 2 cm.) are known. The silk exposed in the net has the
area and dimensions of the surface of this truncated cone.

Methods in Plankton Investigations. 5

6 '

If, now, we complete the truncated cone and denote the side
of the small cone, added for completion, by x, it follows that

x : x-\-i : : r : R;

x = -j; — = 7.619 cm.
K—r

If, now, we imagine the surface of the completed cone

unrolled and spread in one plane (Fig. B), the circumferences

C ( = 2 R n ) and c ( = - 2 r n ) will form arcs subtending an

unknown angle or, and it follows that the circle described by

the radius x ( = = %xn ) is to 2 r n as 360° is to a, or

2x7i 360

2 r 7T a

360 r

a = ;

x
a= 94.5°.

This angle a being known, it is a simple matter to lay off
the pattern for the net. The pattern for the linen head-piece
is constructed in a similar manner. Allowance must be made
along the edges mr and ns (Fig. B) for the longitudinal seam.
It has been our custom to allow 4 mm. upon one margin and
8 mm. upon the other (Fig. 2, Plate I.). The two edges are
brought together and backstitched at a (Fig. 2), and the wider
margin is then turned under the other and felled at b upon
the outside of the net. Thus only a single seam 4 mm. in
width traverses the length of the net. A very fine needle is
used in the sewing, and the line of stitches can be effectually
closed with a light coat of rubber cement. Allowance must
also be made along the edge mn for attachment of the silk
between the linen cone (Plate I., Fig. \,c. b. I.) and the cover-
strip (e. s.) at the seam sm, and for the fastening of the silk,
along the margin rs, between the net clamp (n. e.) and the
head-piece {h. p.) of the bucket. In order to get the net into
the clamp it is necessary to slit the silk at several points to
within a short distance of the line rs (Fig. B).

b. The detachable bucket (Plate II., Fig. 3-5) used by us
differs in several particulars from that described by Apstein
('91, '92, and '96) and also from the one devised by Reighard
('94, p. 26, Plate II.). It copies the Reighard bucket in sub-

6 Illinois State Laboratory of Natural History.

stituting a removable plug for the turncock in the Apstein
bucket, and differs from both in the base and in the manner
of attachment of the silk in the windows.

In form it is a cylinder 7 cm. in height and 4 cm. in out-
side diameter. (Owing to the material available for construc-
tion our bucket measures 4.4 cm. in outside diameter.) It
consists of three pieces : the head-piece, the bucket proper, and
the band clamp.

The head-piece of the bucket (Plate II., Fig. 3, h. p.) is a
cylinder 2 cm. in height, whose upper edge is rounded upon
the inner face. The lower edge is threaded at m (Fig. 3) so
as to screw into the top of the bucket proper, which is corre-
spondingly threaded at n (Fig. 4). The screw is so con-
structed that the inner surface is uninterrupted when the bucket
proper is fully screwed on. The head-piece also bears three
equidistant eyes (Fig. 3, e.), in which are tied the three stay-
lines (s. I.) which pass up to the large, and then to the small,
rings of the net, and finally unite with the draw-line (Plate
III., Fig. 6, d. /.). The position and manner of attachment
of these stay-lines can be seen in Plate II., Fig. 3, and in Plate
III., Fig. 6. The net is clamped on the head-piece by the
circular net clamp (Plate II., Fig. 3, n. c), which is a band
of brass 1 cm. in width. To the ends of the band are attached
wings (w. n. c), which are approximated by means of a
thumb-screw (/. s.). By this operation the silk beyond the
line rs (Fig. B.) is firmly clamped between the brass band of
the net clamp and the head-piece of the bucket.

The bucket proper (Plate II., Fig. 4 and 5) is a brass cylin-
der 5 cm. in height, and of the same diameter inside and
out as the head-piece. In the side of the bucket at a height
of 2 cm. are cut three windows 2.5 X 3.5 cm. These windows
are closed by a band of No. 20 silk held in place by a band
clamp, in which are windows similar to those in the wall of
the bucket. The bucket was constructed from a heavy piece
of brass tubing, the bottom (Fig. 4, b.) being inserted in the
following manner. The tube is turned out to the shoulder
(Fig. 3, sh.) and heated in a jet of steam, and while still hot
the piece of brass from which the bottom (b.) is finished, is

Methods in Plankton Investigations.

«i> '

inserted upon the shoulder. The shrinking of the tube as it
cools holds the bottom firmly in place, and it can then be
completed as shown in Fig. 3. At the center of the bottom
is the outlet of the bucket, which is reamed to hold the taper-
ing plug {p.). Both the plug and the bottom are finished
obliquely to a drip-point (d. p.) at one side. This facilitates
the removal of the last few drops of the catch from the bucket.
The bucket below the bottom of the windows holds about
7 cu. cm. The base (ba.) retains the original thickness
(.5 cm.) and its weight adds to the stability of the bucket.
Since the drip-point does not project below the base the
bucket can be set down, and, owing to the fact that its center
of gravity is low, it is not easily overturned. This is a dis-
tinct advantage where the work must be done in a small row-
boat at the mercy of the waves.

The band clamp (Plate II., Fig. 4 and 5, b. c.) is a sheet
of brass 4.5x15.3 cm., and about .1 cm. in thickness. At
a distance of .75 cm. from the ends the sheet is bent out at
right angles, and a brass bar 4.5 X. 75 X. 25 cm. is soldered
in the angle thus formed (Plate II., Fig. 4 and 5, pi. and//.').
The band is now bent around the bucket and the ends brought
together by means of two screws (sc.) which pass through
the one bar and screw into the other (Plate II., Fig. 5, pi.
and //.')• The windows (Fig. 4, w.) can now be cut through
both the band and the walls of the bucket. The pillar (Fig.
5, pi.) between the windows adjacent to the ends of the clamp
is .5 cm. wider than the other pillars, whose width is about
1 cm. The inner edges of the windows are carefully rounded
so as to afford no lodgment for the plankton. It is also a
convenience to attach the band of silk (Fig. 4, s.) which closes
the windows to the side of the bucket by means of a thin
coat of King's waterproof cement. The band clamp can then
be slipped over the bucket and the silk bound firmly in place
by tightening the two screws (Fig. 4 and 5, sc). The base
also bears an eye (e.) for the line which fastens the bucket to
the carriage at z (Plate III., Fig. 6).

The above-described detachable bucket, devised by the
writer, has certain obvious advantages over the Apstein and

8 Illinois State Laboratory of Natural History.

Eeighard buckets after which it is very largely modeled. Its
advantages are its stability, the drip-point, and the band
clamp, the latter permitting readily the renewal of the silk in
the bucket.

Previous to the adoption of the bucket just described, the
net in which the collections at Havana were made was closed
by a circular piece of silk clamped on the end of a brass
cylinder screwing into the head-piece (Plate I., Fig. 1, h. p.).
The clamp used for this purpose is similar to that
employed to fasten the net to the head-piece. (See Plate
I., Fig. 1, and Plate II., Fig. 3, n. c.) When a collection
had been made the silk circle was removed and, with the plank-
ton condensed upon it, transferred to the killing fluid. This
form of plankton bucket was used by Apstein ('92) on his
qualitative plankton net, and was afterwards described by
Borgert ('96) for a net to be towed behind steam- vessels.

c. The head of the net (Plate I., Fig. 1) is a truncated
cone, at whose upper and lower ends are rings 10 and 25 cm.
in diameter respectively (u. r. and /. ;-.). These rings are
made of No. 5 (American Standard Gauge) brass wire. The
side of the cone (e. b. I.) is made of heavy linen, known in the
trade as " butchers' linen." Its lower edge is joined to the
silk net at the seam (Plate I., Fig. 1, sm.), where it also
meets the cover-strip (e. s.) — a narrow band, made of the
same cloth — which extends over the lower ring (/. r.). In the
upper edge of the cone is bound a heavy cord (cd.) which, in
turn, is fastened to the upper ring (u. r.) bj a series of loops
of strong thread (th.). The upper ring and the cone are sup-
ported by three equidistant wire stays (w. s.). These are
made of No. 8 brass wire and are provided with an eye at
each end. The lower eye (/. e.) embraces the lower ring and
is held in place by small hips soldered upon each side. The
upper eye {u. e.) is attached to the cord (cd.) by a small cloth
strap (st.) and also serves as a point of attachment for a stay-
line (s. I.) which runs from the bucket to the lower end of
the wire stay (w. s.) to which it is fastened, passing from
this to the upper eye (;/. e.) and then to the draw-line (Plate
III., Fig. (J, d. /.).

Methods in Plankton Investigations. 9

& '

2. The Carriage (Plate III., Fig. 6 and 7). — The carriage
for the plankton net is a wooden bar, 100x5x2 cm. It
hears upon one edge two ceiling pulleys (Fig. 6, /. and p.'),
through which passes the carriage rope (c. r.). In order that
there may he no tendency on the part of the carriage to float,
two bars of lead (/.) are inserted in its lower edge, so that it
naturally assumes a position upon the lower side of the rope.
The carriage is so constructed that it may be separated along
the line a b c, thus freeing the net from the fixed carriage
rope. Its two parts are held together by two flat brass hooks
(k.) which enter the staples (s.). The net and the lines per-
taining thereto are attached to the removable part of the
-carriage at four points (w, x, y, a) at which screw-eyes are
inserted, the attachment being made by means of small metal
snaps (sn.). At the anterior end of the carriage a stay-line
(s. I. 4), coming from the end of the draw line (d. /.), is fast-
ened to the screw-eye w. Upon this line comes the main
stress when the carriage is drawn along the rope. The upper-
most of the three stay-lines of the net (s. I. 1) bears a snap
which is fastened to the screw-eye x at the lower anterior
corner of the carriage. This makes it certain that the plane
of the mouth of the net will be kept perpendicular to the line
of progress of the carriage. A snap at y binds the net to the
carriage and another at z supports the bucket.

3. Accessory Apparatus (Plate III.). — The stay- and draw-
lines are of braided linen. The latter is about thirty-five meters
in length and is carried on a hand-reel. It is knotted at inter-
vals of one meter to a point thirty meters from the opening
of the plankton net. The carriage rope is a five-sixteenths
inch braided rope known in the trade as " sash cord." It
does not kink in handling, and if once thoroughly seasoned
is subject to little change when wet and cannot easily be
stretched. This rope is about forty meters in length and is
marked by colored threads at a point exactly thirty meters
(Plate III., Fig. 7, m.) from the opening of the net. The
location of the end knot (Fig. 6, k.) is marked in a similar
manner.

Three sharpened stakes (Fig. 7, b. s., m. s., and e. s.), the

10 Illinois State Laboratory of Natural History.

brace-, main-, and end-stakes, respectively three, four and one
half, and five meters in length, complete the apparatus nec-
essary for making an oblique haul.

4. Operation of the Oblique Haul (Plate III.). — In this
operation two persons are required, an oarsman to handle the
skiff and an operator for the apparatus. The method of pro-
cedure is as follows. The brace rope (Fig. 7, b. r.) is fastened
near the lower end of the brace stake (b. s.) and the latter is then
set as firmly as desired. The main stake (;;/. s.) is then put in
place and the brace rope is tied to it. Next, the carriage rope
(e. ;-.) is fastened. to the main stake (m. s.) at a point 5 to 8 meters
distant from the thirty-meter knot (;;/). The boat is then
rowed away in line with the two stakes and the carriage rope
is unreeled until the end is reached, when it is run through the
pulleys (Fig. 6,/. and p.') of the upper part of the carriage.
The end knot (k.) is then tied and fastened to the rear pulley
(p.') by the release thread (///.). The carriage rope is next
tied to the lower part of the end stake (Fig. 7, e. s.), and at a
point just in front of the anterior pulley (p.) it is bound to
the end stake by the release line (r. I.). The lower part of
the carriage with the suspended plankton net can now be
attached to the upper part, and the end stake is ready to be
placed. When the end stake is set, the carriage line (Fig.
7, e. r.) runs obliquely from the release line to the surface of
the water at the main stake. The net occupies the position n.
(Fig. 7), and having been lowered vertically does not strain
any water in its descent. After placing the end stake the
skiff is rowed to the main stake as the draw-line (Fig. 7, d. I.) of
the carriage is unreeled. A quick jerk upon the carriage rope
snaps the release line (/-. /.) on the end stake, and the slack
in the carriage rope can be taken up at the main stake. The
carriage rope and nee now take the position c. r.' and ;/.'
(Fig. 7), and the thirty-meter knot ;;/ is at the surface of the
water. Everything is now in readiness for making the catch.
At the signal the release thread (th.) which binds the rear
pulley to the end knot is broken by a quick pull upon the
draw-line. The carriage bearing the plankton net is drawn
up the oblique rope the distance of thirty meters in one minute

Method's in Plankton Investigations. 11

5

by the operator, who regulates the speed by the meter knots
on the draw-line and the counting of the oarsman, one count
being given every other second by the watch. By this method
a uniform velocity for the plankton net at all parts of its
ascent and in different hauls is assured, and a very important
source of error in the vertical haul, as it is usually made, is
avoided. The oblique haul is not so complicated as it may
perhaps seem to the reader. With a little practice the whole
operation may be completed in less than twenty minutes.

Whenever a current is present in the body of water exam-
ined, it has been our custom to make the oblique haul across
the current, thus eliminating, so far as may be, its effect upon
the coefficient or straining capacity of the net. In water in
which there is little or no current it is of advantage, in work-
ing in a skiff, to set the apparatus "with the wind." In
waters abounding in vegetation, channels of the length and
width requisite for making the oblique haul were opened from
time to time by cutting out and removing the rank growth of
aquatic plants.

5. Difficulties encountered. — Certain difficulties attended
the operation of the oblique haul. Owing to the turbidity of
the water, in many situations it was practically impossible to
place the apparatus so as to avoid vegetation. Whenever the
plankton net or the ropes strike a submerged plant, a cloud
of flocculent debris is set free in the water and the collection
is fouled. It was only with the greatest labor that channels
could be kept open in the vegetation, for its rapid growth and
its shifting by the wind soon closed any opening that had
been made. Again, the manipulation of the apparatus in
rough weather is somewhat difficult, the waves at times tear-
ing loose the stakes before the completion of the collection.
At periods of high water the strong current and the increased
depth made it impossible to set the apparatus or keep it in
place. This necessitated the substitution of a series of ver-
tical hauls from a floating boat for the customary oblique
method of collection.

The plankton at Havana is subject to extreme local and
seasonal variations, not only in volume but also in composi-

12 Illinois State Laboratory of Natural History.

tion. For example, at one time Cladocera predominate and
at another diatoms are present in vast numbers, and at still
another rotifers constitute practically the whole of the plank-
ton. Observations upon the operation of the net in the midst
of these fluctuations awakened the suspicion that the amount
of water actually strained was subject to considerable varia-
tion, dependent, among other causes, upon the amount and,
more especially, the composition of the plankton. If the
plankton were constant in quantity, kind, and distribution,
the error arising from the progressive clogging of the net as it
traverses the thirty meters would be distributed alike in all of
the catches, and they would still be comparable ; but the exist-
ence of the fluctuations in the plankton just noted and the
consequent variation in the amount of water strained, con-
stitute an important source of error in any deductions based
upon comparisons of catches made under these variable con-
ditions. This source of error is present in the vertical as
well as in the oblique haul. Furthermore, change in the silk
itself consequent upon use adds to the errors due to the fact
that the collection is made by drawing the net through the
water. A series of field experiments (to be described in a
later paper) upon the progressive clogging of the net and the
coefficient of various plankton nets, in a wide range of season
and situation, have abundantly justified our abandonment of
the system of collection in which the net is drawn through the
water for one in which a known quantity of water is put
through the net.

II. THE PUMPING METHOD.

For many years the biological examination of potable water
has been conducted by straining or filtering water delivered
through service pipes at the faucet by pressure due to the use
of a pump.

Giesbrecht ('96) describes the collection of Copepoda in the
Eed Sea by Kramer, who strained the water delivered by the
ship's pump to the bath-tub of an ocean steamer.

Cleve ('96), at the suggestion of Dr. John Murray, collected
plankton on board a steamer in the North Sea by attaching a
silk net to the pump when the deck was washed.

Methods in Plankton Investigations. 13

<b '

Previous to this, Hensen ('87) used the steam pump for
putting known amounts of surface water through the filtering
net. Hensen's quantitative work was, however, based upon
collections made by vertical hauls of the plankton net. Peck
('96), in his work upon the marine plankton of Buzzard's
Bay, obtained water for examination by the Sedgwick -Rafter
method (see Rafter, '9*2, and Twenty-third Annual Report of
the State Board of Health of Massachusetts for 1891, pp.
395-421) by means of a steam-pump connected with a two-
inch hose which was lowered to the desired depth. Beyond
these instances no other applications of the pump to the col-
lection of plankton have come to my notice, and there appears
to be no record of its use in quantitative work by the Hensen
method.

The impossibility of using the vertical haul in shallow
waters, the difficulties in the operation of the oblique haul,
and especially the error involved in the variable coefficient of
the net, have led to the adoption of the pumping method in
the plankton work at Havana.

1. The Pnmp (Plates Y. and VI. ). — The pump we use is
a double acting force-pump, known in the trade as a "Thresher
Tank Pump." It is worked by an upright handle, and has
two cylinders, each 6x9 inches, and throws an almost contin-
uous stream. Its capacity is one cubic meter of water per six
hundred strokes, provided that the water is delivered to the net
without elevation. The stroke is of definite length and its
action is regular, the rate employed being one stroke per sec-
ond. The pump is provided with 20 feet of 2 -inch spiral-
wound suction hose, terminating in a funnel 20 cm. in diam-
eter. The mouth of the funnel is covered with a linen net
of ^-inch mesh to prevent the entrance of stray bits of vegeta-
tion, and the end of the hose is weighted to insure its sink-
ing readily. It was found necessary to paint all exposed iron
in the water chambers of the pump with a thin coat of asphal-
tum to prevent the formation of rust scales.

Before the pump was put in use for regular plankton col-
lections, tests were made of the straining capacity of the silk
under the impact of the current from the discbarge hose. It

14 Illinois State Laboratory of Natural History.

was found that when the water was delivered from a 1-inch
hose into the plankton net and the filtrate refiltered in a second
net of the same silk (No. 20), a considerable quantity of the
more minute forms, Rot if era and Protozoa, were forced through
the meshes of the first net. This led to the adoption of the
l^-inch discharge hose, and of a net devised hy the writer
to reduce the force of the discharge, to protect the silk from
direct contact with the current, and to equalize the pressure
upon the filtering surface.

2. The Net (Plate IV., Fig. 8-10).— The net consists of
the cover with its accessories and the net proper, the two
being so constructed as to he readily separable. From the
under side of the conical copper top to which the hose
is attached hangs the silk net. When in use the net
is supported in a wooden frame, which also serves as a
float. The rim fits into the circular central opening and rests
upon a projecting ledge of the frame (Fig. 8, fl.) in such a
manner that the silk does not come in contact with the wood.
The frame is so proportioned that the net projects about 8 cm.
above the level of the water. Experience has demonstrated
that even when the water is full of silt or the plankton is very
abundant this elevation is sufficient to provide for filtration
without forcing the water into the net by the pump. In ordi-
nary circumstances the water does not rise more than 2-4
cm. above the level of the water in which the net is sub-
merged. Thus practically the whole straining surface is under
water. Two turn buttons (t. b.) hold the net firmly in place
so that it cannot be dislodged by the action of the waves when
the water is rough.

The cover (Plate IV., Fig. 8, cov.) is an obtuse
cone of sheet copper, 33 cm. in diameter and 20 cm. on the
side. The apex bears a curved connector {con.) upon which
the H-inch hose can be slipped. The cover is beaded for
rigidity, and carries two handles (//.) for lifting the net from
the frame. • After the water enters the net two devices are
employed to check the force of the discharge. The first is an
inner copper cone (i. c), with diameter of 13 cm. and side of 10,
placed in the axis of the net immediately below the orifice of

Methods in Plankton Investigations. 15

<b '

the connector. The cone is suspended from the top by means
of three stays (st.), and sheds the water centrifugally against
an inner net (/. n.) of No. 12 silk. This net is hung from a
ring (/-. /.) lixed to the under surface of the cover by three
supports, one of which (t. s.) swings upon the pivot (/>.) and
permits the removal of the net. The inner net conforms to the
proportions of the outer net but is only 27 cm. in diameter at
the top. At its apex is an opening 8 cm. in diameter, through
which plankton caught on the sides can be washed into the
lower part of the outer net.

To secure rigidity the margin of the cover is provided with a
projecting horizontal wing (ti'.), to which is attached the foot
(Plate IV., Fig. 8-10,"/.). This in cross-section is L-shaped,
extending obliquely downward and outward, the oblique and
horizontal arms being respectively 2.5 and .75 cm. in length.
The foot fits into a circular trough (/;-.) 1-1.25 cm. in width
and 2.75 in height. The inner wall (Fig. 9, 10, i. w.) of the
trough is parallel to the oblique face of the foot, against which
it rests when the cover is in place. The cover is held in the
trough by means of four turn clamps (Fig. 9, c), which are
fastened by straps (str.) upon the outer wall (o. w.) of the
trough. When the clamps are released and swing to the posi-
tion c-', the cover can be removed, and the upper margin of the
outer net (Fig. 9, o. n.) can be folded over the inner wall of
the trough. When, now, the cover is replaced, the net is
firmly clamped between the oblique face of the foot and the
inner wall of the trough. (Cf. Fig. 9 and 10.) This method
of attachment permits the ready removal of the net for the
purpose of drying the silk, and at the same time insures a
tight joint.

The net is made of the customary No. 20 silk and meas-
ures 92 cm. on the side. The upper border is faced upon
the outer surface for cm. and upon the inner for 2 cm.
with butchers' linen, so that the wear in the fastening of
the net falls upon the linen, while the silk only is exposed to
the water to be filtered (Fig. 10). To insure the uniform
placing of the margin of the net in the fastening, a heavy cord
(at.) is sewed in the border, against which the angle of the foot

16 Illinois State Laboratory of Natural History.

rests when placed in position. The plankton bucket, with its'-
method of attachment to the net, is similar to that described
for the vertical net.

3. The Method of Operating the Pump. — The pump is
carried in a suitable row-boat, and the suction hose is operated
from the stern by one person while a second attends to the
pump and the net (Plate VI.). In the choice of a location
and in the position of the boat, due regard must be had to the
direction of the wind and the current, if any, so that no fil-
tered water may reenter the pump. In our work in the lakes it
has been our custom to tie the boat to poles set for this
purpose ; but in the river the boat has been allowed to drift
with the current in order to make the collection, so far as may
be, from the same body of water. After the depth is ascer-
tained the suction hose is lowered to within a foot of the
bottom, the pump is thoroughly rinsed, and while still filled
with bottom water the discharge hose is connected with the
net. As the pumping progresses the funnel is raised at regu-
lar intervals ; for example, every tenth stroke, the interval and
the distance raised varying, however, with the total depth of
the water to be traversed. Since the pump is filled with
bottom water when pumping begins, it is necessary to shorten
the first interval by the number of strokes required to fill the
pump and to correspondingly lengthen the last one. In this
manner a vertical column of water of the desired volume may
be pumped through the net. In addition to the vertical catch we
have followed the custom of making one from bottom water and
another from surface water. After the requisite number of
strokes of the pump have been made the hose is disconnected
and the net removed from the frame and thoroughly rinsed
down. The catch is concentrated in the bucket and trans-
ferred to the bottle of alcohol or formalin.

The pumping method has been successfully employed in
freezing weather by attaching a foot- warmer to the side of the
pump and encasing the whole in a wrapping of felt paper.
The foot-warmer burns a cake of specially prepared coal, and
will keep the pump warm during a day's work of ten hours.
A special drain-cock (not shown in Plate Y.) provides for the'

Mel hods in PI a nk ton Investigations. 17

<b '

removal of all water from the cylinders when the pump is not
in use.

4. Advantages of the Pumping Method. — As compared with
methods dependent upon hauling the plankton net through
the water, several points of advantage are to be found in
the pumping method. It is more accurate, since the actual
volume of water strained can he determined, and the changes
in the coefficient of the net due to seasonal and local varia-
tions in the quantity and composition of the plankton and to
alterations in the silk of the net with use are to a very large
degree eliminated. The method is also widely applicable : as
water may be drawn from any desired level, it may be applied
to the problem of vertical distribution ; and it may be used in
very shallow water, in the midst of vegetation, in creeks, in
strong currents, under the ice — in fact, in a wide variety of
situations from which the vertical or oblique hauls are wholly
excluded or to which they are with difficulty applied. Again,
no matter how poor the water may be in plankton, it is always
possible to strain an amount sufficient to furnish enough plank-
ton for measurement. The method is also a comparatively rapid
one, requiring for a plankton collection only about one third of
the time consumed in making the oblique haul.

The pumping method is thus admirably adapted to the
situation with which we deal at Havana, i. e., shallow water
and an abundance of vegetation. It is not, however, limited
in its applicability to such situations, but with the help of a
steam-vessel and a steam-pump it is capable of application to
larger and deeper bodies of water.

III. PRESERVATION AND EXAMINATION OF THE PLANKTON.

1. Preservation. — The living plankton is transferred di-
rectly from the bucket of the net to a wide-mouth two-ounce
bottle, and the sides of the bucket are rinsed down thoroughly
with a spray of 1% formalin to insure the complete removal
of all of the catch. Enough strong alcohol is then added to
the bottle to make a grade of about 75%". Surface and bot-
tom collections are usually preserved in 1% formalin, or in
75% alcohol after killing inpicro-sulphuric acid. The bottles
are all labeled with a gummed slip bearing the accessions'

18 Illinois State Laboratory of Natural History.

catalogue number, designation of the catch (whether surface,
bottom, vertical, or qualitative), station, killing agent, and
date. For convenience in handling they are then arranged
chronologically in racks, each holding six bottles. Data blanks
bearing the catalogue number are rilled out for each station
examination. The locality, date, time of day, the condition of
the sky, the direction and force of the wind, the stage of the river
and the amount and direction of its change in the twenty-four
hours preceding, the depth of the water, its turbidity (measured
by means of a porcelain disk), the disturbance of the surface,
the temperature of the air and that of the water at surface
and bottom, the current, the kind of vegetation and distance
from it, the manner of collection and means of preservation
of the catches made, — all are matters of regular record,
together with any other data peculiar to the collection which
could possibly interest the student of the plankton.

2. Quantitative Examination. — The quantitative exam-
ination of all of the plankton collections made at Havana has
been undertaken by the writer. Determination of the quan-
tity of the plankton by both the volumetric and enumeratiye
methods is necessary, owing to the presence, especially in
flood waters, of a large amount of silt. The gravimetric or
weighing method suggested by Zacharias ('95) is, as Ward
('96) has suggested, objectionable on account of the unknown
and presumably variable amount of water or alcohol present
in the still moist plankton. Many of the planktons at
Havana taken in silt-laden waters contain a considerable
amount of mineral and earthy matter. This constitutes a
further objection to the application of the gravimetric method
to our collections. A combination of the gravimetric and
volumetric method has been suggested by Ward ('96) ), in which
plankton of known volume is dried to a constant weight, burned,
the ash weighed and afterwards digested in concentrated
HC1, and the residue then washed, dried, and weighed. The
amounts of organic matter, of soluble salts (calcareous), and
of silicious matter can then be determined, and thus correc-
tions for sand-laden planktons can lie approximately com-
puted. It is evident that this method cannot be applied to

Methods in Plankton Investigations. 1!»

planktons rich in diatoms nor to the silt-laden planktons from
Havana, for a large part of the silt is debris of organic origin,
and the method above described does not differentiate the
organic material of the plankton from that of the silt. For
the quantitative investigation of these silt-laden planktons we
are thus practically limited to the enumerative method with
such incidental help as may be derived from volumetric
determination.

The volumetric determination has taken two forms, the
settling and the centrifugal methods. The former as used by
us is the same as that employed by Eeighard ('94) and Ward
('96a). The plankton is transferred to graduated tubes and is
allowed to stand twenty-four hours, when the amount of the
plankton settled at the bottom of the fluid, is read by the
graduations upon the tube. The tubes used are the carbon
tubes employed by chemists in the Eggert color test for the
estimation of carbon in steel. Our tubes in most frequent use
contain 25 and 50 cubic centimeters respectively, are about
twelve millimeters in inside diameter, and are graduated to
tenths of a cubic centimeter. For very small planktons
another tube, containing only ten cubic centimeters and
measuring six millimeters in inside diameter, was used. After
a series of measurements in the tubes above described it
became evident that a considerable error was involved in the
method. Kepeated measurements of the same plankton in
the same tube, after standing twenty-four hours, revealed a
considerable variation in the volume, as high as 30% in some
instances. Furthermore, planktons do not settle to an equal
density. Those composed of Rotifera or small Cladoeera (as
Chydorns) pack closely, while others containing filamentous
forms, as Oscillaria or Fragillaria, and those in which the larger
Entomostraea are predominant, settle very loosely. Thus the
determination of the volume of the plankton by the settling-
method does not give a uniform test of the amount of plankton
present. Furthermore, the process is a tedious one, especially
when large numbers of catches are to be handled.

The centrifugal machine (Plate VII.) was finally hit upon
as affording the best solution of the difficulties presented in

20 Illinois State Laboratory of Natural Hist

or

the settling method. In our machine we have utilized the
double arms, aluminum shields, and percentage tubes of the
Purdy Electric Centrifuge. The tubes contain 15 cubic cm.,
are graduated to tenths of a cubic cm., and the conical tips
permit the measurement of small planktons with accuracy.
The arms are borne upon an upright shaft which is driven by
a system of gears turned by means of a crank handle, one
turn of the crank giving 24 revolutions of the vertical shaft.
The direction and the speed are thus easily controlled by the
operator. The machine is clamped firmly to a table when in
operation. All parts of the machine, except those from the
Purdy Centrifuge, were devised by Professor W. H. VanDer-
voort, of the College of Engineering, and were constructed in
the University shops. Planktons are subjected to 2,000 revo-
lutions in two minutes, the motion at first being slow and
frequently reversed. The practical limit of compression by
this machine is thus reached, and successive measurements of
the same planktons show that its action is quite uniform.
The average amount of compression in a wide range of
planktons is about 50%, the volume by the centrifuge
method ranging from 30° o to 70% of that obtained by the
settling method. No discussion is needed to prove that the
more perfect the compression the more accurate are the volu-
metric determinations of the plankton. In this lies the main
argument for the use of the centrifuge in quantitative plank-
ton work. It also permits rapid work and is easily manipu-
lated. Our machine was completed in January, 1896, and
this is, I believe, the first application of the centrifugal
machine to quantitative plankton work. Cori ('96) has de-
vised a simple centrifugal machine for precipitation purposes
in zoological work, but it does not seem to be fitted for quan-
titative determination of plankton.

The machine employed by us was also in use for the precipi-
tation of living plankton from the water when Dolley's paper
('96) was received describing a large and powerful centrifuge,
"the planktonokrit," devised for the same work. It is only by
means of some such machine as this that a complete exami-
nation of the contents of the water is possible.

Methods in Plankton Investigations. 21

The enumerative or counting method involves a recogni-
tion of all of the different organisms composing the plank-
ton and the enumeration of the individuals of each spe-
cies present in a part or the whole of the catch. The number
present under a square meter of surface or in a cubic meter
of water can then be computed. This work is the basis of the
discussion of the seasonal range, local distribution, and
interrelations of the components of the plankton. The
method of counting at present employed by us is that described
by Rafter ('92) as a part of the Sedgwick-Eafter method of
microscopical examination of potable waters. This method
was employed by Professor J. I. Peck ('96), and I am indebted
to him for many kind suggestions on its use. The apparatus
consists of a brass cell, 20x50 mm. and 1 mm. in depth,
cemented upon a glass slide, a 1-cubic-cm. pipette, a mechan-
ical stage, and an area-stop for the eyepiece. After the
plankton to be examined is diluted to the desired degree and
thoroughly stirred, one cubic centimeter is transferred with the
pipette to the cell, in which one cubic millimeter underlies each
square millimeter of the cover-glass. By means of the
mechanical stage any desired cubic millimeter of the cell can
l)e placed in the center of the field. The area-stop is a circle
of black paper to be placed in the eyepiece, which cuts off
all the field except that visible through a square opening at its
center. This opening should be of such a size that with the
objective employed for the counting work exactly one square
millimeter of the cell is subject to inspection.

Ordinarily the counting of from ten to twenty squares
suffices for a fair test of the occurrence of organisms in plank-
ton ; but in the work upon the richly diversified plankton at
Havana we have found it necessary to increase the number to
fifty or even one hundred for the commoner and smaller species,
while for the larger and the rarer forms a great part or even the
whole of the catch must be examined.

Ukbana, Illinois, November 23, 1896.

22 Illinois State Labor a lory of Natural History.

BIBLIOGEAPHY.

Apstein, C.

'91. Ueber die quantitative Bestimmung des Plankton im Siiss-
wasser. In Zacharias's ''Die Tier- unci Pllanzenwelt des Siisswas-
sers." Bd. 1 1.. pp. 255-294. Leipzig 1 .

'92. Das Plankton des Siisswassers und seine quantitative Bestim-
mung. Schrift d. Naturw. Ver. f. Schlesw.-Holstein, Bd. IX., Heft
2, pp. 267-273.

'96. Das Siisswasserplankton, Methode und Resultate der quantita-
tiven Untersuchung. Mit 113 Abbildungen. 200 pp., 5 Tab. Kiel
und Leipzig.

Borgert, A.
'96. Ein einfacbes Netz zum Fischen von Plankton bei schneller
Fahrt. Zeitschr. f. wiss. Mikr., Bd. XIL, pp. 307-312.

Cleve, P. T.
'96. Microscopic Marine Organisms in the service of Hydrography.
Nature, Vol. 55, pp. 89, 90.
Cori, C. J.

'96. Ueber die Verwendung der Centrifuge in der zoologischen
Technik und Beschreibung einer einfachen Ilandcentrifuge. Zeit-
schr. f. wiss. Mikr., Bd. XIL, pp. 303-306.
Dolley, C. S.
'96. The Planktonokrit, a Centrifugal Apparatus for the Volumetric
Estimation of the Food-Supply of Oysters and other Aquatic
Animals. Proc. Acad. Nat. Sei. Phila., 1896. pp. 276-239.
Forbes, S. A.
'94. Illinois State Laboratory of Natural History, Champaign. 111.,
Biennial Report of the Director, 1S93-1894. 36 pp., 17 Pis. Chicago.
Giesbrecht, W.
'96. Leber pelagische Copepoden des Rothen Meeres, gesammelt
von Marinestabarzt Dr. Augustin Kramer. Zool. Jahrb.. Abth. f.
Syst., Bd. IX., pp. 315-328, Taf. 5, 6.
Hensen, V.
'87. Leber die Bestimmung des Planktons, oder des im Meere
treibenden Materials an PHanzen und Thieren. V. Bericht d.
Kommission zu wiss. Untersuchung d. deutschen Meere zu Kiel,
1887. XIL-XIV. Jahrg., pp. 1-107. 6 Taf.Nebst Anhang, pp.I.-NIX.
'95. Methodik der Lntersuchungen bei der Plankton-Expedition.
Mit 111 Kigg. im Text. 260 pp.. 11 Taf. und 1 Karte. Kiel und
Leipzig. (Ergebnisse der Plankton-Expedition der Hum bold t-
Stiftung. Bd. I. B.)
Peck, J.I.
'96. The Sources of Marine Food. Bull. U. S. Fish Coram., Vol.
XV., pp. 351-368, Pis. 64-71.

Methods in Plankton Investigations.

23

Rafter, G. W.
'92. The Microscopical Examination of Potable Water. No. 103,
Van Nostrand's Science Series. 160 pp., 5 Pis., New York.
Reighard, J. E.
'94. A Biological Examination of Lake St. Clair. Bull. Mich.
Fish Comm. No. 4. 60 pp., 2 Pis., and map.
Ward, H. B.

'96. A New Method for the Quantitative Determination of Plank-
ton Hauls. Proc. Am. Micr. Soc, Vol. XVII., pp. 255-260.
'96a. A Biological Examination of Lake Michigan in the Traverse
Bay Region. Bull. Mich. Fish Comm., No. 6. 100 pp., 5 Pis.
Zacharias, O.

'93-'96. Forschungsberichte aus der Biologischen Station zu Plon,

Theil I.-IV. Berlin.
'95. Ueber die Wechselnde Quantitat des Planktons im Crossen
Planer See. Forschungsberichte a. d. Biol. Station zu. Plon, Theil
III., pp. 97-117.

♦EXPLANATION OF PLATES.

Plate I.

Fig. 1. Longitudinal section of plankton net. X L j.
c.b.l. Cone of butchers* linen, s.l. Stay-line.

Fig. 2.

Fig. 8.

cd. Cord. sm.

Seam.

cs. Cover-strip. s. n.

Silk net.

e. Eye. st.

Strip fastening cone to stay

h. p. Head-piece of bucket. th.

Thread.

1. e. Lower eye of wire stay. u. e.

Upper eye of wire stay.

1. r. Lower wire ring. u. r.

Upper ring.

n. c. Net clamp. w. s.

Wire stay.

Seam in silk net. X 2.

a. Backstitch. b.

Fell.

Plate IT.

-Longitudinal section of head-piece of plankton bucket. X 1.

e. Eye. s.

Silk.

h.p. Head-piece. s. 1.

Stay-line.

n. c. Net clamp. t. s.

Thumb-screw.

m. Thread, screwing w.n.c.

Wing of net clamp.

into n of Fig. 4.

*Plates I., II., III., and IV. were drawn by C. A. Kofoid and inked by Miss L. M. Hart.

24 Illinois Slate Laboratory of Natural History.

Fig. 4. — Longitudinal section of plankton bucket. X 1.

■ 6.

Bottom.

pi.

Plata of clamp.

ba.

Base.

pi.

Pillar.

b.c.

Band clamp.

s.

Silk.

'/. p.

1 trip-point.

sc.

Screw.

e.

Eye.

sh,

Shoulder.

n.

Thread, serewin

g

on m,

w.

Window.

Fig. :?.

x-y.

Line of section shown

V-

Plug.

in Fig. 5.

Fn;. 5.— Cross-section of plankton bucket at x-y, Fig. 4. X 1. Letter-

Plate III.

ing as in Fig. 4.

Fig G. — Carriage, with suspended plankton
a b c. Line of separation of s.

carriage. s.l.l,s.l 2,8.1.3.
/in. Bucket.

c. r. Carriage rope. s. I. 4.

d. I. Draw-line. sn.
h. Hook. th.
k. End knot. w. s.
I. Lead. w xy z.

p. Front pulley.
p.' Hear pulley.

Fk;. 7. — Operation of the oblique haul. X ;
h. r. Brace rope. e. s.

b. s. Brace stake. in.
/it. Boat. m. s.

c. r. Carriage rope befoi'e n.

release. n.'

c. r.' Carriage rope after r. I.

release. sur.

d. I. I ) raw-line.

net. X i
Staple.

Stay-lines from the draw
line to net and bucket.
Stay-line to carriage.
Snap.
Thread.
Wire stay.

Screw-eyes for attach-
ment of net.

sos-
End stake.
30-meter knot.
Main stake.
Xet before release.
Xet after release.
Release line.
Surface of water.

Plate IV.

FlG. 8. Plankton net used with the pump, shown in longitudinal
section.

X >,.

b. I. Butchers' linen.

con. Connector.

cov. Cover.

f. Foot.

.//. Float.

h. Handle.

i. c. Inner cone or spreader.

i. n. Inner net.

o. n. Outer net.

p. Pivot for support of ring.

ri. Ring for inner net.

st. Stay for inner cone.

(. I). Turn button.

t. .*>•. Turn support.

tr. Trough.

w. Wins:.

Methods iii Plankton Investigations. 2o

Fi<;. 9. — Rim of cover of net, showing clamp for holding cover in
place. X 1.

c Clamp, in position. i. w. Inner wall of trough.

c'. Clamp, released. o. to Outer wall of trough.

coo. Cover. str. Strap of clamp.

/. Foo.t of cover. w. Wing of cover.

Fie. 10. — Same, showing method of fastening outer silk net; cover
partially removed. X 1.

//. I. Butchers' linen. o. n. Outer net.

cd. Cord.
Other lettering as in Figure 9.

Plate V.
The plankton pump. X iV

Plate VI.
The plankton pump in operation.

Plate VII.
The centrifugal machine. X J^.

Plate I.

cs.
lr.~

Plate II.

•5*.

Plate III.

r-~

±1

£

Plate IV.

'> v' V' " s ' *%/ " **'

Plate V.

*

Plate VI.

Plate VII.

BULLETIN

OF THF.

Jllinois 2 tate Laboratory

OF

NATURAL HISTORY,

Urbana, Illinois.

VOLUME V.

ARTICLE II. — A CONTRIBUTION TO A KNOWLEDGE OF
NOR Til AMERICAN FRESH- \VA TER CYCLOPID.E.

By ERNEST R. FORBES, B. S.

Illinois State Laboratory of Natural History,
URBANA, ILLINOIS.

1897.

State Laboratory of Natural History

LABORATORY STAFF

Professor Stephen Alfred Forbes, Ph.D.,
Director of State Laboratory and State Entomologist.

Charles Arthur Hart,

Systematic Entomologist and Curator of Collections.

Frank Smith. A. M.,
Assistant Zoologist.

Charles Atwood Koeoid, Ph. D.,

Zoologist, and Superintendent of Biological Station.

Charles Christopher Adams. B. S.
Entomological Ass istant.

Ralph Waldo Bralcher, B. S.',

Entomological Assistant.

Mary Jam; Snyder,

Secretary.

Henry Clinton Forbes,
Business Agent and Librarian.

Lvdia Moork Hart,
Artist.

Article II. — A Contribution to a Knowledge of North Ameri-
can Fresh-water Cyclopia" ce.* By Ernest B. Forbes.

INTRODUCTION.

During the past twenty years the fresh-water Copepoda of
North America have received considerable attention from a
small number of pioneer investigators, but as yet no one
has made a careful comparative study of authentic repre-
sentatives of the species described by them. It is my pur-
pose in this paper to make a first contribution to a revision
of the nomenclature of this genus, such as is usually found
necessary when, for the first time, the work of unaffiliated
investigators is brought into careful comparison. I have
embodied in this paper, not a complete revision of the Ameri-
can species of Cyclops, but only such results of my study on
that group as have now been brought to a satisfactory eon-
elusion.

The excellent work of Claus and Schmeil in Germany has
greatly modified our ideas of the comparative value of certain
specific characters; and the revision of the European species
of this genus in Schmeil's monograph! has made it possible
for me to begin a revision of the American species along the
same general lines.

The receptaculum seminis, which has recently come to be
considered as the most important structure for purposes of
specific distinction, has received almost no attention from
American investigators; but after studying this organ in
series of specimens of closely related forms from a great
variety of widely separated situations, I have been forced to
include under the same species name forms which have here-
tofore been considered valid species, and to discard as local
or at the most varietal differences, distinctions which have

*This paper was prepared in the course of undergraduate study at the University
of Illinois, and was accepted by the Faculty of the University June 7. 189", as a
thesis for the degree of Bachelor of Science in Zoology.

HDeutschlands freilebende Siisswasser-Copepoden, I. Teil: Cyclopidae.

28 Illinois State Laboratory of Natural History.

been used for the separation of species by our most emineni
workers.

I have made a vigorous effort to obtain authentic examples
of all the species considered; and while I have been in
general successful, f have been forced in the case of Herriek's
species to depend wholly upon the collections to which I have
had access myself, and the identifications of other men who
have collected in Herriek's localities.

The collections which I have had an opportunity to study
in the preparation of this paper are those of the Illinois
State Laboratory of Natural History, extending over a period
of more than twenty years ; several made under the auspices
of the l". S. Fish Commission in Wisconsin and in the far
West ; collections made in Florida by Mr. Adolph Hempel and
in Manitoba by Prof. L. S. Ross, of Drake University, Iowa,
and kindly loaned me by these gentlemen ; and all of the col-
lections made at the Lllinois Biological Station at Havana,
Illinois. This material is from the following states : Massa-
chusetts, Florida, Ohio, Indiana, Michigan, Wisconsin, Illi-
nois, Kentucky, Iowa, Missouri, Minnesota, Idaho, Wyoming,
Washington, and Oregon, and from Manitoba, in the Domin-
ion of Canada.

The localities represented by these collections are widely
distributed and of great variety. They extend from the
New England states in the northeast to Florida in the south-
east, to Manitoba on the north and to Washington and Oregon
in the northwest, and from the sea-level in Massachusetts
and Florida to some of the highest lakes in the Rocky and
Sierra Nevada Mountains. In these collections are Cyclops
from small temporary points of a few weeks' duration, from
the greatest lakes and rivers in the world, and from a great
number and variety of situations intermediate in character.
They have been made in every season -of the year; and
although the southwestern part of the United States is not
represented, they probably contain nearly all of the American
species of the genus.

The results published in this paper do not, however, repre-
sent an exhaustive study of the distribution of the species

North American FresJi-tvatcr Cyclopidce. 29

treated, and a more careful inspection of the collections
examined would doubtless make evident many interesting
facts with regard to the details of distribution.

I have had, for comparison with our American forms,
named European specimens from S. A. Poppe, Prof. G. 0.
Sars, and Dr. Otto Schmeil. Those from Poppe were received
in 1883 by Dr. S. A. Forbes and represent the following
species : Cyclops agilis, helgolandicus, pulchellus, signatus,
and strenuus. During the present year Dr. Schmeil has
sent specimens of Cyclops fuscus, varicans, leuckarti, albidus,
strenuus, serrulatus, viridis, and phaleratus, while Prof. Sars
has sent to Dr. Forbes examples of the species of the follow-
ing list : Cyclops viridis, nanus, robustus, hyalinus, oithonoides,
albidus, fuscus, v emails, macrurus, gigas, leuckarti, insignis,
bisetosus, fimbriatus, bicuspidatus, a/ffinis, crassicaudis, phal-
eratus, bicolor, scutifer, serrulatus, varicans, dybowskii, l<i-
custris, and strenuus. These authoritatively named European
specimens have given me the opportunity for comparative
studies of American and European Cyclopidse — the first, so
far as I am aware, which have been made in America.

The mere study of American specimens of species first
described from European material has not given me, in many
cases, the data necessary for a critical judgment of the
synonymy of such forms, and I have consequently accepted,
as a rule, the determinations of Claus and Schmeil, whose long
experience and critical and exhaustive work give to their con-
clusions the highest authority.

The genera and subgenera of Clans ('93a, '93c, '93d) seem
to me very convenient subdivisions of this varied genus, and
the species of this paper have, so far as possible, been ar-
ranged under Claus's groups. I find it necessary, however,
to create two new subgenera, Orthocyclpps and Homocyclops,
for the two American species C. modestus and ('.titer. The
descriptions are incomplete, however, because of the lack of
knowledge concerning the males of these two species.

Certain characters used by some of our American investi-
gators for specific distinction have proven unreliable, and a

30 Illinois State Laboratory of Natural History.

brief discussion of their comparative values may be of service
to beginners in the study of this genus.

The number of antennal segments may be depended upon
as fairly constant. It never varies in adult specimens by
more than a single segment, and then only in the case of a
very few species. The length of the antennae, while constant
in some species, is remarkably variable in others, notably in
C. serrulatus. The proportionate length of antennal seg-
ments does not always remain the same in species in which
the antenna is variable as to length. Sensory structures
and the hyaline plates of the distal antennal segments are
reliable characters.

In certain species, C. phaleratus for instance, the propor-
tions of the stylets are quite constant, but in ('. viridis, serru-
latus, and bicuspidatus , the range of variation is very great;
consequently such measurements are not of the highest spe-
cific value. The apical bristles of the stylets are not very
variable as to comparative lengths, but the minute details of
their structure are not constant. This fact is illustrated by
the variation in the shape of the outer apical spine of ( '.
viridis var. brevispinosus (PI. XL, Fig. 1).

The armature of the swimming feet is of considerable value ii i
certain cases, and is constant as a rule. Sometimes, however,
the presence or absence of a spine or seta is not accompanied
by other perceptible differences. The general character of
the armature with regard to strength, etc., may usually be
relied upon ; but I have often seen in a single specimen all
of the gradations between spines and seta^, and it would be
impossible from this character to say which of the two nanus
should be applied.

Of the easily observable structures, the fifth foot is the
most valuable for specific distinction. Slight variations
sometimes occur in the shape of the segments and in the
comparative lengths of spines and setre, but, as a rule,
characters drawn from this appendage are quite constant.

Of all the specific characters, the most valuable are those
derivable from the receptaculum seminis. Unfortunately, it
is often very difficult to see this organ distinctly, especially if

North American Fresh-water Cyclopidce. 31

the specimens have been killed in alcohol ; but this difficulty
is readily avoided by the use of formalin as a preservative.
A 1% solution is amply strong, and the osmosis of fluids is
not rapid enough to rupture the receptaculum, as is the case
when strong alcohol is used. Some slight differences in the
appearance of the receptaculum are due to stage of sexual
activity of the animal. In the case of C. viridis var. insectus
such a difference is noticeable. In Fig. 3, PL XL, the solid
line represents the outline of the empty receptaculum ; the
dotted line, the shape when fully distended.

Through the generosity of Prof. G. 0. Sars and Dr. Otto
Schmeil, I have received much valuable material from Europe,
by means of which I have been able to compare American and
European forms. I wish also to acknowledge the assistance
received from my co-laborers, Messrs. Pi. W. Sharpe and F.
W. Schacht, and also to thank Prof. L. S. Eoss, of Drake
University, and Mr. Adolph Hempel, now of the Museu
Paulista, Brazil, for the courtesies shown me in the loan
and collection of material. A very great part of the credit
for such portions of this paper as may be of value is due to
my instructor, Dr. S. A. Forbes, whose kind supervision and
encouragement have constantly guided and aided me in this
work.

Genus Cyclops 0. F. Muller.
Subgenus Cyclops s. str. Glaus.
Cyclops leuckarti Claus. (PL VIII., Fig. 1-3.)

Cyclops leuckarti, Claus, '57, p. 35, PI. I., Fig. 4; PJ. II., Fig. 13, 14.
Cyclops leuckarti, Schmeil. "92, pp. 57-64, PI. III., Fig. 1-8.
Cyclops leuckarti, Herrick and Turner, '95, pp. 90-98, PI. XVI.;
XVIII., Fig. 1, A-J: XXIV., Fig. 2-0.

This species is of medium size, but is rather more slender
than usual (PL VIII., Fig. 1). The cephalothorax is broadest
at the first segment and tapers conspicuously toward the
posterior end. The length as compared to the breadth is
about as eleven to six.

The abdomen is long and slender, but the stylets are short,
being one third or one fourth as broad as long. They are

32 Illinois State Laboratory of Natural History.

not markedly divergent, and there is no conspicuously broad
space between their points of attachment. The outer apical
seta is delicate and as long as the stylet. Of the remaining
three, all of which are well developed, the middle one is the
longest and the innermost the shortest.

The first antennae are long and slender, terminating at the
middle or end of the third cephalothoracic segment. The last
two segments are both long, but the sixteenth (penultimate)
is the longer of the two. These two segments bear broad
hyaline plates (PI. VIII., Fig. 2). The margin of the one
borne by the sixteenth segment is entire, but the one on the
following segment besides being finely serrate its whole length
is deeply notched near its distal end. This notch is very
characteristic of the species. On the twelfth segment is the
usual sense-club.

The posterior border of the second segment of the outer
maxillipeds usually bears a series of rounded transverse
ridges, which extend in a series from the proximal end of
the segment nearly to the other end. The presence of this
structure seems characteristic of the European form, but may
rarely be entirely absent in American specimens.

The setae and spines of the swimming feet are conspicuously
long and strong. The margin of the connecting lamella of
the fourth pair of feet bears a pair of sharp teeth. The
feet are armed as follows: — First pair: outer ramus, two
spines, four seta? ; inner ramus, one seta, one spine, four setae.
Second and third pairs : outer ramus, three spines, three
seta'; inner ramus, one seta, one spine, four setae. Fourth
pair: outer ramus, three spines, four seta-; inner ramus,
one seta, two spines, two seta-.

The rudimentary foot (PL VIII., Fig. 3) is two-segmented.
The basal segment is short and roughly quadrate, with a long
plumose seta borne on its outer angle. The distal segment is
long and slender. On the middle of the inner side is borne a
long pectinate spine, and at the tip a seta of about equal length.

The receptaculum seminis is large and elliptical, and the
anterior part, from which proceed the canals, is laterally
expanded.

North American Fresh-water Cyclopidce. 33

The egg-sacs are carried at a broad angle from the
abdomen.

In length the female varies, in American specimens, from
.95 to 1.5 mm.

The color is always inconspicuous and may be light blue
or gray.

This is in general a very rare species in America. I have
never, until recently, found it in collections in any great
numbers, but in twos or threes at long intervals. I lately
found it, however, in immense numbers in a collection made
in August, 1896, from Fox River, Illinois. It is found in
just such situations as is C. edax, but usually in very much
smaller numbers. I have seen this species in collections
from Lake Harriet, Minnesota; Delavan Lake, Wisconsin ;
and from Quiver, Flag, and Dogfish lakes, and the Sangamon
and Fox rivers — all in Illinois. It is widely distributed in
the lakes and rivers of America, but has not been reported
from temporary pools.

Cyclops edax Forbes. (PI. IX., Fig. 1-3.)

Cyclops edax. Forbes, '90a, p. 709. PI. III.. Fig. 15; IV.. Fig. 16-19.
Cyclops annulatus, Wierzejski, "92, pp. 237. 238. PI. VI., Fig. 14-1S.
Cyclops leuckarti, Marsh, '93. pp. 209-211, PI. IV.. Fig. 17: V..
Fig. 2-6.

SYNONYMY AND COMPARISON.

This form has been confounded with ('. leuckarti Claus,
from which, however, it is very easily separated by a careful
comparison of specimens.

The original description of this species was incomplete in
that no mention was made of the sense-club on the twelfth
antenna! segment, or of the hyaline plates of the sixteenth
and seventeenth segments. As in ('. leuckarti (Pi. VIII.,
Fig. 2), the plate of the sixteenth segment has an entire edge,
though the plate itself is much narrower. The plate of the
seventeenth segment (PI. IX., Fig. 2) differs markedly from
the corresponding structure in ('. leuckarti. in ('. edax the
edge of the plate is cut by a series of deep oblique notches,
forming teeth which point strongly backward. These notches

34 Illinois State Laboratory of Natural History.

are deepest near the distal end and thence diminish in hoth
directions. The segment itself is deeply excavated within and
the plate merely completes its usual outline, while in ( '.
leuckarti the segment is but slightly excavated and the broad
plate projects far beyond the outline of the segment.

In C. edax the last two segments are equal, while in
C. leuckarti the sixteenth segment is a fourth longer than
the last.

The two pointed teeth of the connecting lamella of the
fourth feet, which are characteristic of C. leuckarti, may
sometimes be present in ('. edax, though they are in this
species not so sharp as in the other and are placed farther
apart.

The transverse ridges of the outer maxillipeds, which
Schmeil describes as characteristic of C. leuckarti, are usually
absent in ('. edax and when present are quite inconspicuous.
They begin, as in C. leuckarti, at the proximal end of the seg-
ment, but soon fade away.

The abdominal stylets in ( '. edax are more divergent than
in C. leuckarti, and are inserted farther apart.

The fifth feet (PL IX., Fig. 3) are markedly different. In
C. edax the two seta- of the distal segment are parallel and
the surfaces to which they are attached are at right angles to
the long axis of the segment. In ('. leuckarti the surface of
attachment of the lower seta is at an angle of about forty-five
degrees to the long axis of the segment. Furthermore, the
whole distal segment is broader in ( '. edax.

There are differences in general proportions and appear-
ances which make it very easy for one well acquainted with
these species to distinguish them at a glance, but these
differences can only be demonstrated by a long series of
measurements. The structure of the receptaculum scminis
is identical in the two species, so far as 1 can tell; but
though the species are undeniably closely related, I think
that on account of the above-mentioned differences they
should be kept distinct.

Cyclops edax may possibly be the same as ( '. leeuwenhoekii
Hoek, which Schmeil has made synonymous with ( '. leuckarti.

North American Fresh-water Cyclopidce. 35

If the figures as published by Hoek are correct, C. edax differs
from ('. leeuwenhoekii in the following particulars : In edax
the labrum has eleven teeth; in leeuwenhoekii it has but ten.
In edax the seventeenth antennal segment is longer than the
sixteenth; in leeuwenhoekii the sixteenth is longer than the
seventeenth. In edax the first foot, outer ramus, bears on the
distal segment two spines and four sets; in leeuwenhoekii the
corresponding segment bears three spines and two sets. In
edax the inner margin of the distal segment of the fifth foot
is not incurved as in leeutvenhoekii. In edax there are never
less than five prominent teeth in the lamella of the seven-
teenth antennal segment; in leeuwenhoekii but three are fig-
ured. The transverse ridges on the maxilliped of leeuwenhoekii
are more prominent, smaller, and more numerous than in
edax.

DISTRIBUTION'.

This form is very abundant and widely distributed in
America. I have found it, among many other places, in col-
lections from the Mississippi and Illinois rivers ; from various
lakes and ponds of Illinois ; from Sister Lake and Lake
Butler in Florida ; from Spirit Lake and Lake Okoboji in
Iowa ; and also from lakes Michigan, Superior, Winnebago,
and Michigamme, and Yellowstone, Delavan, and Cedar
lakes. It was described in 1892 by Wierzejski from the
Argentine Republic under the name of C. annulatus.

SPECIFIC DESCRIPTION".

The cephalothorax is oval, compact, and broadest before
the middle. The first segment is as long as the remainder.
The last thoracic segment is scarcely broader than the first
abdominal.

The first abdominal segment is very long, equaling the fol-
lowing three. The last segment is the shortest and is bordered
by the usual row of spinules. The preceding segments are
bordered posteriorly by coarse serrations, more pronounced
and regular on the ventral than on the dorsal side. The
stylets are one third as wide as long, and in a long series of
measurements of individuals from the most widely separated

36 Illinois State Laboratory of Natural History.

localities this proportion only varied by one thirtieth. The
inner margins of the stylets are filiate. The lateral spine is
a trifle behind the middle ; the outer seta about as long as
the ramus; the inner live sixths the length of the third from
within ; the latter two thirds as long as the second.

The antennae terminate between the end of the second and
the end of the third segments. There is a sense-club and
seta on the twelfth segment. The sixteenth segment is never
longer than the seventeenth. The sixteenth and seventeenth
segments bear hyaline plates (PL IX., Fig. 2), that of the six-
teenth segment being very narrow, with its edge entire, and
that of the seventeenth broader, with its edge deeply notched.
The notches are most pronounced near the distal end and fade
away in each direction. The intervening teeth point strongly
toward the base of the antenna. The segment is excavate on
the inner side, and the hyaline lamella completes the normal
outline of the segment by filling up the depression.

The swimming feet are armed as follows : —First pair : outer
ramus, two spines, four setae; inner ramus, one seta, one
spine, four seta 1 . Second and third pairs : outer ramus, three
spines, three seta-; inner ramus, one seta, one spine, four
seta-. Fourth pair: outer ramus, three spines, four setae;
inner ramus, one seta, two spines, two seta 1 .

The feet of the fifth pair (PL IX., Fig. 3) are two-segmented.
The distal segment bears two parallel setae, the outer one of
which is set at about the middle of the segment. This seta is
most strongly spinulose on the outer side, while the distal one
is plumose on both sides.

The receptaculwm seminis is large and elliptical, the long
axis corresponding to the long axis of the segment. The
lateral canals are connected with the expanded upper portion.
The receptacnlum is almost exactly as in C. leuckarti.

The egg-sacs are elliptical and stand out from the abdomen.

The usual length of the female is 1.2-1.4 mm.

North American Fresh-water Cyclopidce. 37

Cyclops viridis Jurine. (PI. X., Fig. 1-3.)

Monoculus quadricornis var. viridis, Jurine. '20. p. 46, PI. III., Fig. 1.
Cylops viridis, Schmeil, "92, pp. 97-101, PI. VIII., Fig. 12-14.

SYNONYMICAL DISCUSSION.

Though the subdivision of the viridis group here proposed
is not entirely satisfactory and may not be final, still after
long study of more extensive collections than have heretofore
been brought into comparison in America, I have arrived at
some conclusions with regard to the subdivision of the group
which may be of service to any one following me in the study
of the American Cyclopidce.

C. rifi dis occurs in America, so far as I now know, only in
the larger forms of that species. C. ingens (Herrick, '82a)
seems to me the only described form corresponding very
nearly to the European viridis, and 1 therefore regard it as
the American representative of that species. It is considered
by Marsh as equivalent to C. americanus (= ('. insectus), and
Herrick himself says that it is distinguished from this form
only by its greater size. From Fig. 3, PI. XXV., in Herrick
and Turner '95, I judge that C. ingens is synonymous with
( '. viridis, thus representing in America the maximum devel-
opment of the species, as does ('. gigas in Europe.

Dr. Forbes has for years recognized such a form as ('.
ingens, and it is to be found in the temporary ponds of central
Illinois. The species was in 1870 given the manuscript and
label name of ('. levis, but the description was never pub-
lished. This ('. ingens or levis differs from specimens of
viridis received from Sars and Schmeil only in its greater
size, and from specimens of ( '. gigas received from Sars only
in some of the more minute details in the outline of the two
segments of the fifth foot. The two forms gigas and ingens
are undoubtedly typical C. viridis. It is of interest to note
that in both of these large forms the small spine of the fifth
foot is not separate from the segment, but is a process of the
segment itself. Schmeil states that in C. viridis it may or
may not be separated from the segment by a suture. ( '.
ingens is the only form in America having the stylets ciliate

38 Illinois State Laboratory of Natural History.

internally. In the smaller forms most closely related to
viridis, in which the small spine of the fifth foot is always
separate from the segment, the inner border of the stylet is
never filiate, though in rare cases the whole inner aspect of
the stylet seems to be set with the shortest of hairs, only
visible on account of their points of attachment.

The first species closely related to viridis described in
America was C. insectus, described in 1882 by Dr. Forbes.
Later in the same year C. L. Herrick described a very closely
related form under the name of C. parens. This species has
been most profusely figured by Herrick, but his drawings of
the fifth foot are so very different as to make it impossible to
say where it belongs in this most perplexing group. I have
failed in my attempts to obtain authentic examples of ( '.
parens, but have found a few specimens answering to Herrick's
description in a temporary pond in Urbana, Illinois. I can-
not, however, vouch for their identity. In the same collec-
tion I found other specimens differing from those above men-
tioned only in the presence of the additional spine of the first
and fourth feet — the feature separating this form from C.
insectus.

So variable is C. insectus, found, as it is, in an endless vari-
ety of situations and localities, that the lack of a single spine
on the distal segment of the outer ramus of the first and
fourth feet is. not sufficient ground for the distinction of even
a variety, for I find, as does Dr. Schmeil, that the armature
of the swimming feet is not in all species absolutely con-
stant.

In Herrick and Turner '95 (PI. XXXIY., Fig. 5), is a draw-
ing of the fifth foot of ('. parens. This drawing was evidently
made with somewhat greater care than were those on Plates
XX. and XXL, and represents approximately the same ap-
pendage in ('. insectus.

Cyclops amerieanus, described by C. I). Marsh in 1892,
proves on examination of authentic examples to be synony-
mous with C. insectus. Undoubtedly C. amerieanus of Herrick
and Turner is identical with Marsh's form and is consequently
also a synonym of insectus.

North American Fresh-water Cyclopidee. 39

Cragin in 1883 figured a form as C. viridis and stated that
it was found at Cambridge, Mass. This form is C. ins,, -tux.
Cyclops miiangulatus, described as new in the same article, is
also C. insectus, the only apparent difference being a very
slight one in the armature of the swimming feet.

Cyclops brevispinosus, described in 1884 by Herrick, differs
from C. insectus principally in the shape of the outermost
terminal spine of the stylet. In the type of brevispinosus this
spine is very broad, heavy, and knife-like in character. I have
seen considerable variations in the shape of this spine and
have observed all of the gradations between it and the usual
slender spine of C. insectus. I think, however, that C. brevi-
spinosus should be considered as a good variety. The follow-
ing description of ('. viridis is a translation of the description
by Schmeil ('92).

SPECIFIC DESCRIPTION.

"The two axes of the cephalothorax compare about as two
to one ; the ratio of the length of the cephalothorax and the
abdomen is almost the same. The cephalothorax tapers about
equally in both directions; each segment projects laterally
far beyond the following. Seen from the side, the posterior
angles of all the plates of the cephalothoracic segments are
rounded, those of the first and fifth segments being at first
straight, then convexly produced at their ends ; and the
second, third, and fourth segments, in which such promi-
nences are lacking, are slightly lengthened posteriorly.

" The first abdominal segment is but little broadened in its
anterior part. The posterior borders of all the segments are
coarsely serrate, with the exception of the last, which bears
a fringe of spinules.

"The stylets are often two, three, or even four times as long as
the last abdominal segment. The innerborder is always ciliate.
The lateral spine is set beyond the middle of the outer edge.
The outermost of the apical bristles (all of which are nar-
rowly plumose) is not, as is the case with most species,
changed into a spine, and is exceeded in length by the inner-
most. Both middle bristles are well developed, but their

40 Illinois State Laboratory of Natural History.

proportional lengths arc not entirely constant. Usually the
smaller of the two is as long as the abdomen, and the larger

exceeds it in length. They are often of exactly the same size,
and often the difference is considerable.

" The first antennae are seventeen-segmented, usually reach-
ing hack only to the posterior border of the first cephalo-
thoracic segment. The last three segments are but little
longer than those immediately preceding. The twelfth seg-
ment bears a projecting sense-club.

"The remaining pairs of appendages, with the exception of
the rudimentary feet, present no notable characters and hence
arc systematically valueless. Spinous armature of swim-
ming feet, 2. 3. 3. 3.

"The rudimentary foot (PL X., Fig. 2) is two-segmented.
The extraordinarily broad basal segment bears on the Lower
outer angle a long plumose hair. On the lower border,
immediately at the inner angle of this segment, is attached
the relatively small distal segment, which bears at its distal
end a plumose hair and at the inner margin a very minute
spine.*

"The receptaculum seminis (PI. X., Fig. 3), the two small
lower divisions of which terminate in the lateral canals, are
usually covered by the larger, more or less heart-shaped upper
division. Exact knowledge of the structure of this organ is
usually first possible after the application of delicate pressure.

" The large elliptical egg-masses stand off from the abdomen
at a very sharp angle.

"The color is usually a dirty green, seldom a light brown.
In a pool in Diemitz I met with quite fire-red examples.

" The size is very variable. With individuals 1.5-2 mm. one
finds others 2.5, 3, 4, or even 5 mm. in length.

"The clearest and simplest recognition characters are the
rudimentary feet and the structure of the receptaculum
seminis."

*In a foot-note Schmeil states that Claus, Hoek, Richard, and Lande, consider

this spine as a process of (he segment, that Ulianin figures it as separated from the
segment by a suture, and that lie. Schmeil, had observed it both ways.

North American Fresh-water Cyclopidce. 41

Var. brevispinosus Herrick.
(PL XL, Fig. 1 and 2.)

Cyclops brevispinosus, Herrick. '84, p. 148, PL S. Fig. 7-11.
Cyclops brevispinosus, Marsh, '93, pp. 205-206, PI. IV., Fig. 11. 12.
Cyclops brevispinos us, Herrick and Turner. '95, p. 95, PI. XXIII.,
Fig. 1-4: XXIV., Fig. 7-12.

This species of Herrick's, which I reduce to a variety, is dis-
tinguished from typical C. viridis, as follows: 1. By the
form of the outer terminal spine of the stylet, which is short,
broad, and knife-like. This form of spine is connected in
series (PL XL, Fig. 1) with the slender spine of the variety
insectus. 2. By the fifth foot (PL XL, Fig. 2). In this
appendage the small spine is never a part of the segment as it
may he in the European viridis and always is in the American
form. This spine is also longer than in riridis and is lanceolate
in shape. 3. By the armature of the swimming feet. The
spines of these appendages are extravagantly long and heavy.
While at first sight these differences might seem sufficient for
the complete separation of the two forms, the distinguishing
characters are in most species of Cyclops so variable that it
seems to me best to consider brevispinosus as merely a variety.

The receptaculum sen/in is is as in insect us.

I find this variety in collections from Lakes Michigan,
Manitoba, Okoboji, (Iowa) ; and from Lake Winnebago, Green
Lake, and Lake Geneva in Wisconsin; from Swan Lake in
Montana, and Lake Pend d'Oreille in Idaho ; from the Detroit,
Calumet, and Illinois Livers; and from Sand, Fox, Quiver,
Dogfish, Phelps, and Thompson's lakes — all in Illinois. It
is never especially abundant but seems to lie quite generally
distributed.

Var. insectus Forbes.
(LI. XL, Fig. 3-6.)

Cyclops insectus, Forbes, '82a, p. U49. PI. IX.. Fig. i>.
Cyclops parous, Herrick, *S2a, p. 229, PI. VI.. Fig. 12-15.
Cyclops insectus, Herrick. '84, pp. 151, 152, PJ. U, Fig. 9.
( 'yclops viridis, Cragin, '83, p. 68, PI. IV., Fig. 8-16.
< 'yclops unlangulatus, Cragin, '83, p. 71, PI. IV., Fig. 17.
Cyclops insectus, Sehmeil, '92, p. 95.

4'2 Illinois State Laboratory of Natural History.

Cychps parcus, Marsh, "93, pp. 208, 209. PJ. IV.. Fig. Ki: V.. Fig. 1.
Cyclops americanvs, Eerrick and Turner, '95, pp. 91, 92, PI. XIV..

Fi<;. 1-9.
Cyclops parcus, Herriek and Turner. '95, pp. 03, 94, PJ. XX.. Fig.

12-15: XXI.. Fig. 22: X X 1 1 1.. Fig. 8 : X X X .. Fig. 1-8.

This variety represents in America the smaller members of
the viridis relationship. It is distinguished from viridis in
Europe by the lack of cilia on the inner side of the stylets,
by some slight differences in the shape of the receptaculum
seminis (PI. XL, Fig. 3), and by the different shape of the fifth
foot. The receptaculum seminis differs in that the upper part
is larger in proportion to the segment in insectus and is some-
what different in outline. In the fifth foot (PI. XL, Fig. 4
and 5), the outer distal angle of the basal segment is much
less produced and the spine of the distal segment, which is
always separated from the segment by a suture, varies in
length from a minute barbule to a long heavy spine, longer
than the segment itself. The armature of the swimming feet
(PI. XL, Fig. 6) is not constant and is not in C. viridis useful
even as a varietal distinction.

This brief diagnosis includes under the varietal name
insectus, forms which differ superficially to a marked degree,
but after continuous work for more than a year with very
large collections from all parts of the United States I have
been forced to throw ^hem all together for the simple reason
that there is no one set or combination of characters suffi-
ciently invariable to subdivide the group.

The antenna^ of this variety usually terminate at or before
the end of the first cephalothoracic segment, but in examples
from Alturus Lake, they reach the middle of the second seg-
ment.

The stylets of this variety vary considerably in proportions.
The following series of measurements of nine specimens
shows the extent to which this character varies. On the left
is a list of the localities from which the specimens were
obtained and on the right are figures representing the propor-
tion between the length and breadth of the stylet.

North American Fresh-water Cyclopidcc. 43

Pond, Normal, 111.. . . . . 63:9

Creek, AVyoming, . . . . 52:11

Lake Winnebago, . . . . 52:8

Lake Superior, . . . . 44:9

Illinois River, . . . . . 40:9

Mississippi River, . . . . 37:8

Pond, Urbana, 111 34:7

Pond, Yellowstone Park, . . 33:9

Slough, Manitoba, . . . . 33:9

There is a very peculiar semicircular indentation of the
outer side of the basal segment of the inner ramus of the
fourth foot often present in this variety, hut it may he
entirely absent or only present in a slight degree of develop-
ment. Whatever the function of this peculiar indentation, it
does, not seem to he essential to the animal.

The fifth foot varies but little in the basal segment but the
distal segment is peculiarly variable. In one extreme, which
reaches its highest development in the Illinois River, this seg-
ment is very short, its length compared to its breadth being
as 3.5 to 3, and its sides strongly outcurved. The small
spine is situated some distance from the end of the segment
and is very small indeed. Examples of the other extreme
are common in the ponds of central Illinois. In these the
last segment is much longer, its length being to its breadth
as 9 to 5. In this form the spine is parallel to and often
longer than the segment.

The shape of this distal segment seems to vary independ-
ently of the other specific characters, and all gradations
between the two forms may be found in a single pond. These
variations are not demonstrably connected with the environ-
ment.

The receptaculum seminis (PL XL, Fig. 3) is, when fully
distended, of the shape represented by the dotted line, but
otherwise may have the shape outlined by the solid line. As
will be seen by comparing this figure with that of the recep-
taculum seminis of C. viridis (PL X., Fig. 2), the anterior
portion of the receptaculum is comparatively larger in insectus
and its outline as a whole is somewhat different.

I find that the coloring of this species is so variable that no

44 Illinois State Laboratory of Natural History.

dependence can be placed upon it for purposes of distinction.
This variety may be wholly red or blue or greenish or it
may even be colorless.

It is found everywhere in the United States and Canada
where Cyclops have been collected, and no situation seems to
be free from them. In Illinois by far the greater portion of
the Cyclops of the small ponds and temporary pools and
puddles belong to this species.

Cyclops bicuspidatus Claus. (PL XII. , Fig. 1-4.)

Cyclops bicuspidatus, Claus, '57, p. 209.

Cyclops pulchellus, Sars, '63, pp. 246,247, PI. XI., Fig. 6 and 7.

Cyclops navus, Herrick, "82a. p. 229, PI. V.. Fig. 6-13, 15-17.

Cyclops tfwmasi. Forbes. "82a. p. 649.

( 'yclops bicuspidatus, Suhmeil, '92, pp. 75-87, PJ. II., Fig. 1-3.

Cyclops minnilus, Forbes, '93, p. 247.

Cyclops serratus, Forbes, '93, pp. 247, 24S.

Cyclops Jbrbesi, Herrick and Turner, '95, p. 104.

SYNONYMICAL DISCUSSION.

This immensely variable and widely distributed species is
represented in the United States by a number of forms which
have been described by our most reliable zoologists as species
new to science. As more complete series of collections from
the United States have been studied, it has become evident
that these forms are so closely connected in series, that dis-
tinctions which a few years ago were considered as specific
must be cast aside and the whole group united under the
name of the European form.

With regard to Cyclops thomasi Forbes, I must agree with
Dr. Schmeil that there is no need of considering this form as
even a variety. A close study of the type specimens of
( 'yclops tli mil <i si reveals a number of small differences between
it and Cyclops bicuspidatus as described by Dr. Schmeil, but
they agree almost exactly with other descriptions, by European
investigators, of forms included in Dr. Schmeil's synonymy of
C. bicuspidatus Clans. Only a single specimen of the form
as described by Dr. Schmeil has been found by me in collec-
tions from this country. This single individual came from a

North American Fresh-water Cyclopidce. 45

pond at Wood's HolJ, Mass. The most conspicuous difference
between this form and C. thomasi is a slight one in the shape
of the fifth foot.

In the Illinois River are specimens which bridge over com-
pletely the gap between C. bicuspidatus and Herrick's C.
navus, and I see no reason for considering navus as a good
variety.

Cyclops minnilus Forbes is distinguished from C. thomasi
by different proportions alone. It is one of the western rep-
resentatives of this species and has been collected in the
lakes and rivers of Wyoming.

Cyclops serratus Forbes is found in the same situations as
C. minnilus, from which it is distinguished by a slight differ-
ence in the armature of the feet and by the fact that the
vertical comb of spines of the furcal stylets is but poorly
developed. The name xerrtrfiiH being already in use, Herrick
renamed the species forbesi. This is the most elongate of
the American representatives of the species.

SPECIFIC DESCRIPTION.

This is a long and slender species (PI. XII., Fig. 1) with
seventeen-segmented antennae, oval cephalothorax, slender
abdomen, very long and slender caudal stylets, and but two
developed seta; to each stylet. The longer of these setaa is
about twice as long as the shorter. The cephalothorax is
widest at about the middle. In specimens from the eastern
United States the posterior angles of the cephalothorax are
not usually prominent except in the case of the last segment,
where they are laterally produced. In the far western speci-
mens the posterior angles of all the segments are prominent.
The peculiar appearance of the cuticle caused by circular pits
or depressions which Dr. Schmeil mentions, is rarely present
in the iVmerican form. I have found it in greatly varying
degrees of definiteness in specimens from Lake Superior
and from Wyoming.

The first segment of the abdomen of the female (PI. XII.,
Fig. 1) is emarginate behind the prominent lateral angle.
This segment is about as long as all the others together. The

46 Illinois State Laboratory of Natural History.

posterior margins of all but the last segment are irregularly
and often very obscurely serrate. The last segment is
bordered posteriorly by the usual row of spinules. The sty-
lets are often slightly outcurved. In relative length to breadth
they vary from four to one to nine to one, but the usual
proportion is as seven to one. The inner of the two longer
seta; is as long as the entire abdomen, and the outer of the
two but half that length. The extreme outermost of the
terminal setae is two thirds as long as the inner. On the
outer side of each stylet, a little behind the middle, is
placed a spine surrounded at its base by a ring of spinules,
and at one fourth of the distance from the proximal end is a
vertical comb of small spines (PI. XII., Fig. 2). This
character seems to be invariably present.

The antennae of the female are moderately robust and
terminate in the American forms between the posterior end
of the first segment and the middle of the third segment.
A sense-club is borne on the distal end of the twelfth segment.
No hyaline plate is present on the terminal segments. The
last three segments gradually increase in length toward the
distal end of the antenna, the antepenult being two fifths
the length of the last. The two segments preceding the
former, taken together, are shorter than the last segment,
and about equal to the penultimate.

The armature of the thoracic legs is as follows : — First pair :
outer ramus, two spines, four seta ; inner ramus, one seta,
one spine, four seta. Second pair : outer ramus, three spines,
four seta ; inner ramus, one seta, one spine, four seta.
Third pair, exactly like second. Fourth pair : outer ramus,
three spines, four seta; inner ramus, one seta, two spines,
two seta.

The fifth pair (PI. XII., Fig. 3) are two-segmented, the
basal segment about as long as broad, with a plumose seta at
the outer angle, the terminal segment roughly cylindrical, at
least twice as long as broad, with two terminal seta-, the outer
of which is as long as the seta of the preceding segment and
the inner a little more than half that length. This inner seta
is sometimes spine-like.

North American Fresh-water Cyclopidce. 47

The receptacidum seminis (PI. XII., Fig. 4) is regular in
outline, the anterior border being a low arch extending com-
pletely across the segment. The posterior portion is much
deeper and about half as wide. The broad spermal canals
arise from the anterior angles. The porus is exactly between
the two anterior angles.

The egg-sacs are usually small and round in the specimens
from large lakes ; otherwise they are elliptical and very large.

The usual length of the female is 1-1.4 mm.

This species is very widely distributed in America. It has
been found in Massachusetts and Wyoming and in all the
intervening territory. It is the common pelagic species of the
Great Lakes, but also occurs in large numbers in our ponds
and rivers. Inhabiting, as it does, such a great amount of
territory and such a variety of situations, it is not strange
that it proves to be a very variable form. The Massachusetts
form is exactly as described by Dr. Schmeil. In Wyoming
this species is very much more slender in all its details,
though not differing markedly in any other way from the type.
Between these two extremes in location are a great number
of intermediates in form. The fifth foot is rather variable,
but I note no variation in the shape of the receptacidum semi-
nis. The vertical combs of spines on the stylets are always
present, but are not always conspicuous in the Western speci-
mens. Although the most attenuate specimens examined
were usually from large lakes and the most robust from ponds,
I find that no other generalizations are possible with regard
to the character of the specimens in connection with the
nature of the situation — probably on account of the frequent
transfers of individuals from one of these situations to another.

Subgenus Macrocyclops Claus.
Cyclops albidus Jurine. (PI. XIII.)

Monoculusquadricornis var. albidus, Jurine.'20, p. 44. PI. II.; Fig. 10,11.
Cyclops gyrinus, Forbes, '90a, pp. 707-709, PI. II., Fig. 9; III.. Fig. 14.
Cyclops signatus var.tr mi icoi-tiis^Herrick and Turner, "95. pp. 106.107,

PI. XV.. Fig. 5-7: XX.. Fig. 1-7; XXXIII., Fig. 1,2.
Cyclops albidus, Schmeil, '92, pp. 128-132, PI. I., Fig. 8-14b; PI. IV.,

Fig. 15.

48 Illinois State Laboratory of Natural History.

SYNONYMY.

Since the description of C. gyrinus by Dr. Forbes in 1890,
more careful descriptions of C. albidus in Europe and fur-
ther studies in America have established the identity of the
two forms. The original description of C. gyrinus was in-
complete in that the presence of the sense-club and hyaline
plates was not observed.

SPECIFIC DESCRIPTION.

This is a stout, heavy species, with a strongly arched
cephalothorax, which, as a whole, is usually quite elliptical,
with the lateral angles of the segments almost invisible ;
but in specimens from Manitoba I find the cephalothorax
shaped much as in C. viridis. The first segment in these is
subspherical, narrowing posteriorly, and the posterior end
of the second segment is much broader than the anterior
end. All of the lateral angles are prominent. The breadth
of the first segment compared with its length is as ten or
eleven to twelve.

The dorsum of the fifth segment in this species is or-
namented by three or four transverse rows of spinules, the
posterior one of which borders the segment.

The abdomen is thick and heavy. The first segment in the
female is but slightly enlarged and tapers very little. The re-
maining segments are cylindrical. The stylets are short and
slightly divergent. The proportion of the length to the
breadth of the stylet varies but slightly. The usual ratio is
two and one half to one. The apical bristles are all well
developed, the third from without being the longest, and the
innermost three times as long as the outermost.

The first antenna? of the female are seventeen-segmented,
and reach to the first abdominal segment. The distal three
segments bear hyaline plates, entire, except for minute ser-
rations on the distal half of the plate of the seventeenth seg-
ment. The twelfth segment bears an unusually large sense-
club.

The swimming feet are armed as follows : — First pair :
outer ramus, four spines, four setae; inner ramus, one seta,

North American Fresh-water Cyctopidce. 49

one spine, four seta?. Second and third pairs : outer ramus,
four spines, five seta ; inner ramus, one seta, one spine, four
setas. Fourth pair: outer ramus, three spines, five setge;
inner ramus, one seta, two spines (inner naked and movable),
two setae (distal one minute).

The fifth foot is two-segmented. The basal segment is two
thirds as wide as long, its outer margin straight, its inner,
convex and minutely hairy. The distal end is truncate, with
a very long seta at the outer distal angle. The second seg-
ment is about as long as the preceding is wide, lobed in the
middle and trisetose, the outer seta shorter than the inner,
and the latter about half as long as the median.

The anterior portion of the receptacuhim seminis is kidney-
shaped and the posterior is two-lobed. The lateral canals
are attached to the lower portion.

The usual length of the female in America is from
1.26-1.4 mm., but it seems to be much greater (2.5 mm.) in
the European representatives of the species.

The color, which is blue or green, is distributed in dark
bands with nearly colorless intervals on the thorax, the last
abdominal segment and stylets, and on the second, third,
ninth, and tenth antennal segments.

This species is very generally distributed, having been
found in all the localities in America from which collections
have been examined. It is not common in temporary ponds,
but I have several times noted its occurrence in wells.

Subgenus Homocyclops n. subgen.

Cephalothorax very robust. Antennas seventeen-segmented.
Eami of swimming feet three- segmented. Fifth feet one-
segmented, bearing one spine and two seta'.

Cyclops ater Herrick. (PI. XIV., and PI. XV., Fig. 1-3.)

Cyclops ater, Herrick, "82a, p. 228, PJ. III.. Fig. 9-12.
Cyclops ater, Marsh, '95. pp. 13, 14, PJ. VI., Fig. 1-4, 6, 12.
Cyclops ater, Herrick and Tinner, '95, pp. 89, 90, PL VII., Fig.
11. 12; XII., Fig. 9-12; XXL, Fig. 13-15, 17, IS.

The cephalothorax is peculiarly short and broad. Its first

5 Illinois State Laboratory of Natural History.

■

segment is very large and is twice as long as the remaining
segments together. The posterior edges of all the segments
are smooth.

The abdomen is relatively small, but is broad in proportion
to its length. It tapers but little and the first segment is
scarcely at all enlarged. The segments, except the last, are
finely and irregularly notched posteriorly. The caudal stylets
are short, the length to the breadth being about as three to
one. They are not ciliate within. In the small number of
specimens which I have had an opportunity to examine there
is no outer lateral spine, but at the usual place for this spine,
a little behind the middle, is a shallow scar where a spine
might at some time have been attached. I do not think,
however, that this is probable. The terminal setae are all
well developed, but the median pair is much longer than the
lateral ones. The innermost seta is slightly longer than the
outermost. Of the four, the second from the inside is the
longest.

The first antenna' of the female are seventeen-segmented
and reach to the middle or end of the second cephalothoracic
segment. The twelfth segment bears the usual seta and
sense-club, though the latter organ is unusually small. The
fourteenth segment bears an especially long, strong seta.
The last two segments (PI. XV., Fig. 1) bear a narrow hyaline
lamella which projects some distance beyond the end of the
seventeenth segment. The edge of this plate is entire. Of the
last three segments, the middle one (sixteenth) is the longest.

The seta? of the swimming feet are short and stout. The
armature is as follows : — First pair : outer ramus, three
spines, five seta? ; inner ramus, one seta, one spine, four
seta?. Second and third pairs : outer ramus, four spines, five
seta? ; inner ramus, one seta, one spine, four seta?. Fourth
pair : outer ramus, three spines, five setae ; inner ramus,
one seta, two spines, two setae.

The fifth feet (PI. XV., Fig. 2) are one-segmented and bear
one strong spine and two seta' each. The spine is about one
third the length of the seta?. The inner seta, that is the one
next the spine, is borne on a conical projection from the

North American Fresh-water Cyclopidcc. 51

body of the segment. Neither the seta? nor the spine seem
to be provided with hairs or spinules.

The receptaculum seminis (PL XV., Fig. 3) is of an unusual
and very characteristic shape. The anterior part is small,
and its outline is marked by two anterior and two lateral
rounded prominences. The posterior part consists of a
median lobe, partially divided posteriorly, and two curved
lateral lobes from which lead the lateral canals. The porus
is in the median part connecting the upper and lower divisions.

The egg-sacs are of the usual size and shape.

In length the female varies from 1.77 to 2.88 mm.

The color is unusually variable. It is commonly dark blue
or green but may be gray or red. The deep color and large
size make this a conspicuous species.

Herrick says that it is widely but sparingly distributed over
the Mississippi Valley. Marsh reports it from Rush, Round,
St. Clair, Intermediate, Twenty-sixth, and Susan lakes in
Wisconsin. I have noted its occurence in collections from
Thompson's, Quiver, Flag, Phelps, and Dogfish lakes near
Havana, Illinois.

Subgenus Orthocyclops n. subgen.
Antenna? sixteen-segmented. Rami of swimming feet, three-
segmented. Fifth feet three-segmented, distal segment bear-
ing two apical seta?.

Cyclops modestus Herrick. (PI. XV., Fig. 4, and PI.
XVI., Fig. 1-3.)

Cyclops modestus, Herrick, '83a, p. 500.

Cyclops modestus, Herrick and Turner, '95, pp. 108, 109, PI. XXI.,

Fig. 1-5.
Cyclops modestus, Marsh, '93, pp. 213, 214, PI. V., Fig. 10-13.
Cyclops capilliferus, Forbes, '93. pp. 248. 249. PI. XL., Fig. 14-17:

XLL. Fig. 18.

SYNONYMY AND DISTRIBUTION.

By a study of the type specimens of Cyclops capilliferus I
find that they agree almost completely with Herrick's descrip-
tion of C. modestus. The descriptions differ with respect to

52 Illinois State Laboratory of Natural History.

the position of certain spines of the feet, but this is really a
difference in description rather than in characters. I find
also that specimens collected in "Wyoming agree exactly with
the Illinois representatives of the specie.-.

I have noted its occurrence in collections from Quiver, Dog-
fish, and Thompson's lakes, and from the Illinois River,
near Havana, 111. ; from the Sangamon River, in Champaign
county, Illinois; and from Grebe Lake in Yellowstone Park.
Marsh reports it from Rush Lake, Wisconsin, and Herrick finds
it in Cullman county, Alabama, and in Minnesota lakes. I
have never found it in temporary ponds nor in any of the
Great Lakes. From the situations in which it occurs I judge
that this species seeks shallow, weedy water rather than
pelagic situations. It is not an especially rare species, hut I
have never found more than a very few individuals in a single
collection.

SPECIFIC DESCRIPTION.

The cephalothoracic segments are closely articulated and
the sides regularly convex. The first segment is longer than
usual and the fourth is semicircularly excavate behind. The
posterior edges of the first three segments are irregularly
notched and the fourth is smooth. The length of the cepha-
lothorax is to its breadth as two to one.

The abdomen is long, slender, and cylindrical, and is pecu-
liar in lacking the usual fringe of spines on the posterior edge
of the last segment. The posterior edges of the other seg-
ments are likewise smooth. The anterior end of the first
segment is but little enlarged. The segments diminish regu-
larly in length from first to last. The caudal stylets are about
twice the length of the last segment and four times as long as
broad. The lateral seta is placed a trifle beyond the middle
of the ramus. Behind the lateral spine the stylet is pecu-
liarly excavate. The outer terminal bristle, which is set
farther forward than in most species, is a short, sparsely
plumose seta, but the other three seta- are well developed. Of
these three the middle one is considerably the longesi and
the inner one slightly shorter than the outer.

North American FresJi-zvater Cyc'opidce. 53

The antennae are regularly sixteen-segmented, though
Herrick mentions having notes on a similar form in which
the antennae are seventeen-lsegmented. They reach to the
middle of the second cephalothoracic segment. On the third,
tenth, and thirteenth segments are remarkably long, heavy
seta?. The antenna (PL XVI., Fig. 1) is given a characteristic
appearance by the conspicuous seta on the third segment
and a sharp change in direction between the third and fourth
segments. The last segment is much shorter than the one
preceding.

The seta? of* the three-segmented legs are long and slender.
The distal segments of the third and fourth pairs of legs turn
inward in a way peculiar to this species. The legs are armed
as follows : — First pair : outer ramus, four spines, four seta' ;
inner ramus, six seta?. Second pair : outer ramus, four spines,
five seta? ; inner ramus, six seta?. Third pair : outer ramus,
three spines, five seta?; inner ramus, six seta?. Fourth pair:
outer ramus, three spines, five seta?; inner ramus, one seta,
two spines, two seta?.

The fifth foot (PI. XVI., Fig. 2) has three freely movable
segments, though the basal one is small. The second seg-
ment bears one seta without, and the third segment bears two
seta? — both at the tip. The outer seta is apt to be bent inward
across the inner one. These feet are usually large and placed
very close together.

The receptaculum seminis (PL XVI., Fig. 3) is very much
as in Cyclops bicuspidatus Claus. It is nearly elliptical in
outline, and only a small part of the anterior end extends
farther forward than the suture in which the porus is situated.
The lateral canals lead from the anterior part.

The egg-sacs are long and narrow and lie close to the
abdomen.

In length this species does not vary to any marked degree
from an average of 1.2 mm.

The coloring is most beautiful, varying from violet to
purple. It is evenly distributed, and is quite persistent in
specimens preserved in formalin.

54 Illinois State Laboratory of Natural History.

Subgenus Eucyclops Claus.
Cyclops serrulatus Fischer. (PI. XVII., and PI. XVIII.,
Fig. 1-3.)
Cyclops serrulatus and (J. serrulatus var. montanus, Brady. '78, Vol.

I., pp. 109-111, PI. XXII., Fig. 1-14.
Cyclops serrulatus and C. serrulatus var. elegans, Merrick, '81, PI. <,».

Fig. 17-19; PI. Q ; . Fig. 10.
Cyclops serrulatus, Schmeil. '92, pp. 141-14U, PJ. V.. Fig. 0-14.

SYNONYMY, VARIATION, AND DISTRIBUTION.

This is one of the most common and widely distributed of
American ( 'yclops. It occurs almost everywhere between
Maine and California and from Florida to Manitoba.

Herrick's variety elegans is based on such variable charac-
ters that no one acquainted with the species throughout its
range could for an instant consider this form as worthy of a
varietal name, especially since the measurements and descrip-
tions of the type and the variety are contradictory as pub-
lished in his "Synopsis of the Entomostraca of Minnesota."
Herrick says that the variety is distinguished from the type
by its greater size and by the elongation of the antennae and
caudal stylets; but gives 1.5 mm. as the length of the type,
and 1.34 as that of the larger variety. In Europe the largest
specimen on record measured 2.2 mm. in length, much more
than Herrick's large variety. As to the length of the antennae,
I find that this varies immensely and quite independently
of other variations in proportion. Below is a series of meas-
urements of seven egg-bearing females of this species, from
widely separated situations and exhibiting its variability.
Further study of a much larger number of specimens has
convinced me that there are no varietal distinctions possible
among the American representatives of this species, unless
for convenience we arbitrarily separate off the extreme forms.
With the exception of the specimen from Thompson's Lake,
each individual is fairly representative of the species as found
in its own locality.

North American Fresh-water CyclopiUce.

55

Locality

Length to breadth
of caudal stylet

Antenna terminates

Length

Breadth.

Portage La Prairie.
Manitoba

.078:. 018=4. 3:1

Before end of
tirst segment.

.7

.252

Urbana 111

.027:. 015=1. 8:1

End of first
segment.

.54

.198 '

072:. 0225 =3. 2:1

End of first
segment.

.792

.324

Thompson's Lake,
I]]

.075:.01S=4.2:1

End of third
segment.

.72

.216

Pelican Creek, Wyo.

.087:. 03=2. 9:1

Middle of second
segment.

.8S2

.324

Wood's Holl, Mass..

.111:. 027=4.1:1

Middle of third
segment.

.882

.36

Lake Geneva, Wis. .

.24:. 027=8. 9:1

End of third
segment.

1.426

.45

It is also my opinion that Brady's variety montanus should
be considered as merely a variation of the typical form.

SPECIES DESCRIPTION.

The cephalothorax (PL XVII.) is quite regular in shape,
being almost exactly elliptical in outline. Its segments
are closely joined and its lateral outlines smooth. The fourth
segment is deeply excavated behind and is usually bordered
by fine sharp teeth or by long hairs.

The abdomen (PL XVII., and PL XVIII., Fig. 1) is broad
in front, but narrows so rapidly posteriorly that the greater
part of the first segment is as narrow as the slender segments
following. Behind the enlargement of the first segment the
abdomen tapers very little. The last segment is bordered
posteriorly by the usual row of spinules, and the preceding
segments by fine sharp serrations. The stylets are commonly
about straight, but are occasionally strongly outcurved and
divergent. Their length to breadth varies from 1 : 1.8 to 1:9
but 1 : 4 is the commonest proportion. A row of spinules,
spines, or curved hooks marks the outer border of each stylet
and extends from its base to the point of insertion of the outer
apical spine, near the posterior end. These projections in-

56 Illinois State Laboratory of Natural History.

crease rapidly in length at the posterior end and lade away
in front. The male does not have this character, and adult
females are very rarely found without it. Of the four apical
bristles the middle two arc well developed. The inner one
of this pair is much longer than the outer. The innermost
of the four is a very slender seta. The outermost varies in
character from a long seta bordered externally by harbules
and internally by long slender cilia, to a long strong spine
serrate on both sides. It may be anywhere from one half
to four fifths as long as the stylet.

The first antennae are twelve-segmented. Dr. Schmeil
notes the presence of a minute sensory bristle on the ninth
segment in the place occupied by the sense-club on the
twelfth segment of seventeen-segmented antenna?. It is
very inconspicuous indeed. The last three segments are
usually very long and are armed on the inner side by hyaline
plates.

The usual armature of the swimming feet is as follows : —
First pair : outer ramus, three spines, live seta* ; inner
ramus, one seta, one spine, four seta?. Second and third
pairs : outer ramus, four spines, five seta j ; inner ramus,
two spines, four seta?. Fourth pair : outer ramus, three
spines, five seta?; inner ramus, one seta, two spines, two
seta.

The fifth foot (PI. XVIII., Fig. 2) is one-segmented and
plate-like. On the inner side is a very strong serrate spine.
At the tip, borne on a cone-shaped projection, is a very long
slender seta, parallel to the spine. On the outer side i> a
delicate little seta projecting outward at a considerable angle.

The receptaeulum semi7iis (PL XVIII., Fig. 3) is almost com-
pletely divided into an anterior and a posterior part, by a
median constriction. The porus is situated in the middle of
this narrow connecting part. The lower half extends down
into the narrow part of the first abdominal segment. The
spermal canals are attached to the receptaeulum at the outer
angles of the lower part.

The egg-sacs are usually long, with many eggs, but some-
times contain only a few, arranged in a spherical mass.

North American Fresh-ivater Cyclopidce. 57

Ordinarily the egg-sac tapers to a sharp point at the lower
end, and stands out from the abdomen at a wide angle.

The size is remarkably variable. In Europe, the length
varies from .883 to 2.2 mm. In America I have measured
specimens varying in length from .54 to 1.47 mm. A com-
mon length is .9 mm.

Cyclops prasinus Fischer. (PI. XIX., Fig. 1 and 2, and

PI. XX., Fig. 1 and 2.)

Cyclops pr a stmts, Fischer, '(iO. pp. C52-654. PI. XX., Fig. 19-26a.
Cyclops fliiviatllis, Ilerrick, '82 a. p. 231, PI. VI I.. Fig. 1-9.
Cyclops magnoctavus, Cragin, "83, pp. 70.71, PI. III.. Fig. 14-23.
Cyc/ups prasinus, Schmeil, '92. pp. 150-15G. Pi. V., Fig, ]-5.
t )/c lops fluviatilis, Ilerrick and Turner. '95, pp. 114. 115, PJ. XXVI.,
Fig. 1-8; XXX., Fig. 1.

SYNONYMY AND DISTRIBUTION.

On account of the great difficulty in determining the struc-
ture of the receptaculum seminis of C. prasinus, this organ
has escaped study in the American representatives of this
species, and although Marsh had noted a general resemblance
of Herrick's C. fluviatilis to Yosseler's ('. pentagonus (C.
prasinus Fischer), he did not consider these as identical. By
a careful study of a large number of specimens of C. fluviat-
ilis from Illinois, Florida, and Wisconsin, I find a complete
agreement in the characters of the receptaculum seminis of C.
prasinus and C. fluviatilis and in all other specific characters
as well.

I have noted the occurrence of ('. prasinus in collections
from Sister Lake, Florida ; Long Lake, Adams county, 111. ;
ponds and temporary pools at Urbana, 111. ; Illinois Piiver at
Havana, 111. ; Phelps, Flag, and Thompson's lakes in Ful-
ton county, 111. ; Dogfish and Quiver lakes in Mason county,
111. ; and from Lake Geneva, Wisconsin. Ilerrick reports it
from Lake Minnetonka, Minn., and from an estuary of the
Mississippi. Marsh finds the species in Lakes Erie, Michi-
gan, and St. Clair, and in fifteen smaller lakes of Michigan
and Wisconsin. Cragin found it in ditches at Cambridge,
Mass.

58 Illinois State Laboratory of Natural History.

It is thus, in all probability, quite generally distributed
over the eastern and central United States, but I have not
found it in collections from the far AVest. It occurs in all
situations from great lakes and rivers to temporary roadside
puddles of but a few weeks' duration.

SPECIFIC DESCRIPTION.

This minute species has a slender cephalothorax which is
very nearly elliptical in outline. The first segment is regu-
larly convex anteriorly and is unusually long. The posterior
borders of the segments are entire. The lateral edges of the
last segment are fringed by a row of the finest hairs.

The abdomen is long and slender and tapers but little.
The enlargement of the anterior segment is slight. The pos-
terior borders of all the abdominal segments are very finely
serrate. The stylets are short and divergent but are not
themselves outcurved. The lateral spine is inserted just
beyond the middle of the stylet. The inner and outer apical
bristles are very short and delicate, the inner one, the longer
of the two. Only the middle pair of setae are well developed,
and the outer of these is three fourths the length of the inner.

The first pair of antennae (PI. XIX., Fig. 2) of the female are
twelve-segmented and often reach quite to the first abdominal
segment. The seventh, eighth, and ninth segments are very
long. The last three segments are curved and the last four are
freely movable. Schmeil states that the ninth segment bears
a sense-club. I do not find it present in the American repre-
sentatives of the species, although there is a minute sensory
bristle on the end of the tenth segment. The last three seg-
ments bear a hyaline plate whose edge is entire.

The spines and setae of the three- segmented swimming feet
are very long and slender. The armature is as follows : —
First pair : outer ramus, three spines, five seta' ; inner ramus,
six setae. Second pair : outer ramus, four spines, five setae ;
inner ramus, six setae. Third pair armed like second. Fourth
pair: outer ramus, three spines, five seta-; inner ramus,
one seta, one spine, three setae.

The fifth foot (PL XX., Fig. 1) is one-segmented and bears

North American Fresh-water Cyclopida?. 59

three bristles. The inner one is a ciliate spine while the other
two are plumose sette. The middle one of the three is borne
at the tip of a cone-shaped process. The inner edge of the
foot is bordered by a row of minute hairs.

The receptaculum seminis (PI. XX., Fig. 2) is most peculiar
and characteristic. It consists of two parts, anterior and
posterior, separated by the suture marking the original division
of the first abdominal segment. The upper part consists of
two S-shaped canals, one on each side of the median line,
extending across the abdomen. The inner ends which point
downward, fuse in a thicker portion connecting the anterior
division with the posterior. The part of the receptaculum
behind the suture consists of two lateral sacs, which connect
with each other and with the upper part of the receptaculum
at the same point. In the middle of this common part is the
porus. The outer ends of the tubular portion are slightly
enlarged ; otherwise the diameter is uniform. The structure
of this organ has never before been observed in the American
representatives of Cyclops prasinus.

The egg-sacs contain few ova and are closely adherent to
the abdomen.

The length of the female varies from .48 to .7 mm.

The color is unusually variable. The prevailing color of
European specimens seems to be green. I have seen both
blue and pink individuals. Herrick says that the color varies
from deep indigo to greenish brown.

Subgenus Paracyclops Claus.
Cyclops phaleratus Koch. (PI. XX., Fig. 3.)

Cyclops phaleratus, Koch, '35-41, Heft 21, pp. 8, 9. PI. IX.
Cyclops perannatus, Cragin, '83, pp. 72, 73, PI. I., Fig. 0-18.
Cyclops phaleratus, Schmeil, '92, pp. 170-178, PJ. VIII., Fig. 1-11.
Cyclops phaleratus, Herrick and Turner, '95, pp. 120, 121, PL XVII. ,

Fig. 1-7 ; XVIII., Fig. 2-2d ; XIX.. Fig. 1; XXI., Fig. 6-10.
Cyclops phaleratus, Marsh, '95, pp. 19, 20.

DISTRIBUTION.

In America this species is rare, though evidently widely
distributed. I have noted its occurrence in collections from
the Illinois River at Havana, 111. ; a pond at Urbana, 111. ;

60 Illinois State Laboratory of Natural History.

Delavan Lake, Wisconsin ; Quiver Lake, 111. ; Green Lake,
Wisconsin ; Cedar Lake, 111. ; and a slough at Portage La
Prairie, Manitoba. Marsh reports it from Lake St. Clair ;
and from Twenty-sixth Lake, Pigeon Paver, and Intermediate
Lake, Michigan. Cragin describes this species as Cyclops
perarmatus from Glacialis Pond, Cambridge, Mass. It is a
littoral rather than a pelagic form and where occurring in
large bodies of water it is found only in the marginal vegeta-
tion.

SPECIFIC DESCRIPTION.

The cephalothorax is broad and elliptical. The first seg-
ment is longer than the remainder. The chitinous covering
of the fifth segment, which in all other species of this genus is
composed like the four preceding cephalothoracic segments
of a dorsal and ventral plate, is in C. pkaleratus like the
chitinous covering of the abdominal segments in that it con-
sists of but one piece. The ventral portion of the posterior
border of this segment is set with a row of fine teeth, evanes-
cent in the middle. About the rudimentary feet are several
rows of fine spinules.

The abdomen is large and cylindrical, and very little smaller
than the last cephalothoracic segment. The first segment
tapers very little. The posterior borders of the first, second,
and third abdominal segments of the female are finely serrate.
The last segment is very short and the spines on its posterior
border are especially long and strong.- The profusely spinose
stylets are short and broad and taper very rapidly. On the
ventral side of each ramus is a row of long spinules, extend-
ing from the middle line of the anterior border to the point
of insertion of the lateral spine. From this point on, the
rami taper much more rapidly. The inner border of the
stylets is ciliate* and the whole inner aspect may be spinose.
The outermost apical bristle, which is placed high up on the
side of the stylet, is short, and plumose on both sides. The
inner bristle is very slender and is about as long as the outer.
It is plumose on the outside only.* The two median bristles

* Incorrect in figure.

North American Fresh-water Cyclopid(2. 61

alone are well developed. The inner one of this pair is from
two to three times as long as the outer. Except for the outer
side of the outer one of the pair, the anterior third of each is
naked. The remainder is usually sparsely plumose.

The antennae of the female may be either ten- or eleven-
segmented and reach only a little beyond the middle of the
first cephalothoracic segment. In the ten-segmented antenna
the seventh segment bears a delicate sensory hair at its
distal end. This hair is borne on the eighth segment of the
eleven-segmented antenna.

The second antennae are short and proportionately broad.
On the outer side of the second segment is a double row of
spinules. On the upper border of this segment is a spine
and a fringe of spinules. This spine and the shortest one at
the end of the third segment are very peculiar. Both are
strongly curved near the tip, and the inner side of this curve
is fringed by a comb-like row of teeth.

The three-segmented swimming-feet are strongly armed
and their outer borders bear rows of long spinules. The
armature of the distal segments is as follows : — First pair :
outer ramus, three spines, five setae ; inner ramus, one spine,
four setae. Second pair : outer ramus, four spines, four setae ;
inner ramus, one spine, four setae. Third pair : outer ramus,
four spines, five setae; inner ramus, one spine, four setae.
Fourth pair: outer ramus, three spines, five setae; inner
ramus, one seta, two spines, two setae.

The rudimentary feet are lateral rather than ventral and
consist of mere flange-like processes. They are connected
by a row of strong serrations extending across the ventral
side of the segment. Each foot is armed by three subequal
spines, one naked and the other two plumose.

The receptaculum son in is consists of two sections, which
extend as two narrow bands across the segment. The porus
is situated on the median line where the two divisions unite.

The egg-sacs contain many eggs and are closely appressed
to the abdomen. Schmeil calls attention to the fact that the
oviducts, which in all other species are contained wholly
within the cephalothorax, in ('. phaleratas extend as blind

62 Illinois State Laboratory of Natural History.

sacs as far back in the abdomen as the anterior border of
the third segment.

The female varies in length from .9 mm. to 1.26 mm., and
the male is usually about .2 mm. shorter. The largest
specimens measured came from Portage La Prairie, Manitoba.

This is a beautifully colored species. The ground color is
reddish brown. The second cephalothoracic segment, the
last abdominal segment with the stylets, the swimming feet,
and the last segment of the first antennae are sky-blue. A
yellow spot surrounds the eye.

The egg-sacs are dark blue or black.

The best character for the ready recognition of this species
is its strong superficial resemblance to the genus Cantho-
camptus.

GENERAL DISTRIBUTION OF CYCLOPS IN NORTH AMERICA.

Of the eighteen species and three varieties of Cyclops which
have been reported as occurring in North America, but three
species and two varieties, namely, ater, modestus, and edax,
and varieties insectus and brevispinosus of viridis are char-
acteristic of America, while the remaining fifteen species and
one variety are common to both Europe and America.

Probably bicuspidatus, serrulatus, viridis, albidus, and edax
might be found in any state in the Union, so general is their
distribution.

In the Great Lakes by far the most abundant species are
bicuspidatus and edax. Often either one or the other of these
two species will constitute nearly the whole of the crustacean
plankton.

Collections from the high lakes and ponds of the Northwest
usually contain Cyclops, often in considerable numbers, but
they are never present in such great quantities as is the genus
Diaptomus and the Cladocera. The commonest of these
mountain forms are as follows: bicuspidatus, viridis var.
insectus, serrulatus, and albidus, though viridis var. brevis-
pinosus, bicolor, dybowskii, modestus, and edax have been
found in such situations. In collections from Crater Lake,
Oregon, I found a very few specimens of albidus and ser-

North American Fresh-water Cyclopidce. 63

rulatas. This lake is in the Cascade Mountains and is the
highest lake of its size in the world.

As very few observations have been made on the Cyelopidse
of rivers, I examined a continuous series of collections made
in the Illinois Eiver at the Illinois Biological Station, ex-
tending from May to September, 1896. In the first of these
collections bicuspidatus was the predominating form, but it
soon disappeared entirely, its place being taken by viridis
var. insectus. From this time throughout the summer insectus
was by far the most abundant form. Edax, viridis var.
brevispinosus, leuckarti, prasinus, semdatus, and vari cans were
common in the collections, while Jimbriatus var. poppei, viridis,
modestus, bicolor, albidus, and phaleratus were of rare occur-
rence.

LIST OF NORTH AMERICAN SPECIES.

Below is a list of the fresh-water Cyclopidre reported from
America. I have myself seen all of the species of this list
except those herein credited to Herrick.

Genus CYCLOPS.

I. Subgenus Cyclops s. str. Claus.

1. Cyclops leuckarti Claus.

This is a rare species throughout the north central States.

2. Cyclops insignis Claus, fide Herrick.

Herrick has found at Long Island a form which he identi-
fies as this species.

3. Cyclops edax Forbes.

This is a very common species in the Great Lakes and in
the waters of the north central States, Florida, and Wyoming.
It occurs in Argentina, South America.

4. Cyclops oithonoides Sars^/zWt' Herrick.

I regard the occurrence of this species in America as very
doubtful.

5. Cyclops dybowskii Lande.

A rare species found only in the small mountain lakes of
Wyoming and in a temporary pond at Urbana, Illinois.

64 Illinois State Laboratory of Natural History.

G. Cyclops viridis Jurine.

Either the typical form or its varieties occur everywhere
in the fresh waters of the United States. It is the commonest
form of the temporary ponds.

a. var. brevispinosus Herrick.

b. var. insectus Forbes.

7. Cyclops bicuspidatus Glaus.

This species is of the widest range and greatest abundance.
It is the commonest Cyclops in the Great Lakes.

8. Cyclops vernalis Fischer.

Occurs in small numbers in Lake Geneva, Wisconsin.

II. Subgenus Macrocy clops Clans.

9. Cyclops fuscus Jurine.

Occurs sparingly in the ponds and lakes of Wisconsin,
Michigan, Illinois, and Massachusetts.

10. Cyclops albidus Jurine.

Rather a common species throughout the whole range of
the genus.

III. Subgenus Homocyclops n. subgen.

11. Cyclops ater Herrick.

Very rare throughout the Mississippi Valley. Also in Lake
St. Clair (Kofoid).

IV. Subgenus Orthocyclops n. subgen.

12. Cyclops mod est us Herrick.

An uncommon species in the lakes and streams of Wyo-
ming, Alabama, and the north central States.

V. Subgenus Microcyclops Claus.

13. Cyclops bicolor Sars.

Rare in Wyoming, Illinois, Wisconsin, Michigan, and Min-
nesota.

14. Cyclops varicans Sars.

A fairly common species throughout the range of Cyclops
in North America.

North American Fresh-water Cyclopidce. 65

VI. Subgenus Eucyclops Claus.

15. Cyclops serrulatus Fischer.
Very common everywhere.

16. Cyclops prasinus Fischer.

Abundant in all sorts of waters in the Mississippi Valley,
Massachusetts, and Florida.

VII. Subgenus Paracyclops Claus.

17. Cyclops phaleratus Koch.

A rare species in Manitoba, Massachusetts, Alabama, and
the north central States.

18. Cyclops Jimbriat us var. poppei Rehberg.

A rare species in Manitoba, Alabama, and the north central
States.

19. Cyclops ajjinis Sa,vs,Jide Herrick.

If this form occurs in America it is very rare, and limited
in its distribution.

66 Illinois State Laboratory of Natural History.

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'48. Conspectus Crustaceorum qua 1 in Orbis terrarum circumnaviga-
tion e, Caroli Wilkes e Classe Reipublica? Fo?derata2 duce. col-
lectorum. Proc. Am. Acad. Arts and ScL. Vol. I., pp. 149-155.

Eusebio, J. B.
'88. Recherches sur la faune des eaux du Plateau Central. Le
Faune Pelagique des Lacs d'Auvergne. Trav. Labor. Zool. Girod,
T. I., pp. 1-29, PL I.

Fischer, S.
'60. Beitriige zur Kenntniss der Entomostraceen. Abhandl. d. kgl.
bayerisch. Acad. d. Wissensch., Bd. VIIL, Abth. III., pp. 645-682,
Taf. XX.-XXII.

Forbes, S. A.
'76. List of Illinois Crustacea, with Descriptions of Xew Species.

Bull. 111. State Lab. Nat. Hist,, Vol. I., Xo. 1, pp. 3-25.
'82. On the Food of Young Whitefish (Coregonus). Bull. U. S.

Fish Comra., Vol. L. pp. 269, 270.
'82a. On some Entomostraca of Lake .Michigan and Adjacent

Waters. Am. Nat,, Vol. XVI.. pp. 537-543, 640-650. Pis. VIIL. IX.

Nor tli American Fresh-water Cytlopidee. 69

'87. The Lake as a Microcosm. Bull. Peoria Sci. Ass'n, 1887. 15 pp.

'90. Preliminary Report upon the Invertebrate Animals inhabiting
Lakes Geneva and Mendota. Wisconsin, with an Account of the
Fish Epidemic in Lake Mendota in 1884. Bull. U. S. Fish Coram.,
Vol. VTIL, pp. 473-4S7.

'90a. On some Lake Superior Entomostraea. Ann. Rep. U. S. Comm.
Fish and Fisheries, 1887, pp. 701-717, Pis. I.-IV.

'93. A Preliminary Report on the Aquatic Invertebrate Fauna of
the Yellowstone National Park. Wyoming, and of the Flathead
Region of Montana. Bull. U. S. Fish Comm., 1891, pp. 207-258,
Pis. XXXVII.-XLII.

Fric (Fritsch), A.
'72. Die Krustenthiere Bohmens. Archiv der naturw. Landes-
durchf. Bohmen, Band 11., Abth. IV., pp. 203-269.

'95. Uber Schmuckfarben einiger Siisswasser-Crustaceen. Bull.
Internat" 1 Acad, des Sci. de l'Empereur Francois Joseph I., Classe
des Sci. Math, et Xat. II. 7 pp., 2 colored plates.

Fritsch (Fric), A., u. Vavra, V.

'92. Vorlaufiger Bericht liber die Fauna des Unter-Pocernitzer- und
Gatterschlager Teiches. Zool. Anz., XV. Jahrg., No. 382, pp. 26-30.

'94. Untersuchungen fiber die Fauna der Gewiisser Bohmens. IV.
Die Tierwelt des Unterpocernitzer und Gatterschlager Teiches als
Resultat der Arbeiten an der iibertragbaren zoologischen Station.
Arch. d. naturw. Landesdurchf. v. Bohmen. Bd. IX., Nr. II. 123 pp.

Fric, J. A.
'82. Note preliminaire sur rontogenie de nos Copepodes d'eau
douce. Zool. Anz., V. Jahrg., No. 121, pp. 498-503.

Garbini, A.
'94. Primi materiali per una Monografia limnologica del Lago di

Garda. Bull, della Soc. Entom. It., Anno XXVI., pp. 1-50.
'95. Appunti di Carcinologia Veronese. Estratto dal Vol. LXXL,
Serie III., Fasc. I., dell' Accademia di Verona. 91 pp.
Giesbrecht, W.
'81. Die freilebenden Copepoden der Kieler Fohrde. Ber. d. Kom.
z. w. Unters. d. deutsch. Meere in Kiel, pp. S7-168, Taf. I.-XII.
Gruber, A.

'78. Die Bildung der Eiersiickchen bei den Copepoden. Zool. Anz.
I. Jahrg.. p. 247.

Guerne, J. de
'87. Notes sur la faune des Acores. Diagnoses d'un Mollusque, d'un
Rotifere, et de trois Crustaces nouveaux. Le Naturaliste, 1887.
7 pp.

70 Illinois State Laboratory of Natural History.

'87a. La faune des eaux donees des Acores et le transport des ani-
nianx a grande distance par l'intermrdiaire des oiseanx. Compt.
rend, de la Soe. Biol., Seance du 22 oet., 1887. 4 pp.

'88. Excursions zoologiques dans les lies de Fayal et de San Miguel
(A9ores). Campagnes seientifiques du Yacht monegasque l'Hiron-
delle. Troisieme Ann. (1887). pp. 7-110.

Guerne, J. de, et Richard, J.
'89. Sur la faune des eaux douces du Groenland. Compt. rend, de

l'Acad. des Sci., 25 mars, 1889.
'89a. Xote sur les Entomostraces d'eau douce recueillis par M. Charles

Rabot dans la Province de Nordland, Norvege septentrionale.

Bull de la Soe. zool. de France. T. XIV.. pp. 27-31.
'91. Entomostraces, Rotiferes,etProtozoaires proven ant des reeoltes

de M. E. Belloc dans les etangs de Cazau et de Hourtins (Gironde).

Bull, de la Soe. zool. de France, T. XVI., pp. 112-115.
'91a. Sur quelques Entomostraces d'eau douce de Madagascar.

Bull, de la Soe. zool. de France, T. XVI., pp. 223. 224.
'91b. Entomostraces recueillis par M. Charles Rabot en Russie et

en Siberie. Bull, de la Soe. zool. de France, T. XVI.. pp. 232-236.
'92. Cladoeeres et Copepodes d'eau douce des environs de Rufisque.

Mem. de la Soe. zool. de France. T. V.. pp. 526-538.

'92a. Voyage de M. Charles Rabot en Islande. Sur la faune des
eaux donees. Bull, de la Soe. zool. de France, T. XVII., pp., 75-80.

'92b. Sur la faune pelagique de quelques lacs des Hautes-Pyrenees.

Assoc, franc,, pour l'avanc. des Sci., Congres de Pau, seance du 19

sept. 3 pp.
'93. Sur la faune pelagique des lacs du Jura francais. Compt. rend.

de l'Acad. des Sci. 3 pp.

Hacker, V.
'95. Uber die Selbstiindigkeit der vaterlicheu und miitterlichen
Kernbestandtheile wahrend der Embryonalentwicklung von Cy-
clops. Arch. f. ruikr. Anat., Bd. 46, pp. 579-618,Taf. XXVII1.-XX X.

Hartog, M. M.
'88. The Morphology of Cyclops and the Relations of the Copepoda.
Trans. Linn. Soe. London, Vol. V., Part L, pp. 1-46, Pis.. l.-IV.

Hartwig, W.
'93. Verzeichniss der lebenden Krebsthiere der Provinz Branden-
burg. Statt haudschriftl. Mitteilungen herausgeg. v. Markisehen
Prov.-Mus. der Stadtgemeinde Berlin. Pp. 1-44.

NortJi American Fresh-water Cyclopid<z. 71

'94. Die lebenden Krebstiere der Provinz Brandenburg. Nachtrag
zu meinem "Verzeiehniss" von 1893. " Brandenburgia." Monats-
blatt der Gesellsch. f. Heimatkunde der Prov. Brandenburg zu
Berlin, Nr. 7, Okt., 1894, pp. 165-169.

Hay, W. P.
'92. The Crustacea of Indiana. Proc. Ind. Acad. Sci., 1891, pp.
147-151.

Heller, C.
'71. Intersuchungen iiber die Crustaceen Tirols. Ber. des med.-
naturw. Yereins in Innsbruck, 1 Jahrg., pp. 67-96, Taf. I., II.

Herrick, C. L.
'79. Microscopic Entomostraca. Seventh Ann. Rep. Geol. and
Nat. Hist. Surv. Minn., pp. 81-123, Pis. I -XXI.

'82. Habits of Fresh-water Crustacea. Am. Nat., Vol. XVI., pp.

813-816.

'82a. Papers on the Crustacea of the Fresh Waters of Minnesota.
Tenth Ann. Rep. Geol. and Nat. Hist. Surv. Minn., pp. 221-255,
P1S.I.-XI.'

'83. Ileterogenesis in the Copepod Crustacea. Am. Nat., Vol. XVII.,
pp. 208-212.

'83a. Heterogenetic Development in Diaptomus. Am. Nat., Vol.
XVII., pp. 381-389, 499-505, Pis. V.-VII.

'83b. Types of Animal Life selected for Laboratory Use in Inland
Districts. 33 pp.. 1 PI. Minneapolis.

'84. A Final Report on the Crustacea of Minnesota included in the
Orders Cladocera and Copepoda. Twelfth Ann. Rep. Geol. and
Nat. Hist. Surv. Minn., pp. 1-191.. Pis. A-V.

'87. Contribution to the Fauna of the Gulf of Mexico and the
South. List of Fresh-water and Marine Crustacea of Alabama,
with Descriptions of the New Species and Synoptical Keys for
Identification. Mem. Deuison Sci. Ass'n, Vol. I., No. I., pp. 1-56,
Pis. I.-VII.

Herrick, C. L., and Turner, C. H.
'95. Synopsis of the Entomostraca of Minnesota. Geol. and Nat.
Hist. Surv. Minn., Zool. Series, II. 525 pp., 81 Pis.

Hoek, P. P. C.
'76. Zur Kenntniss der freilebenden Siisswasser-Copepoden der
Niederliindischen Fauna. Nied. Arch. f. Zool., Bd. 111., Heft II..
pp. 127-140, Taf. VII.-IX.

'78. De vrijlevende Zoetwater-Copepoden der Nederlaudsehe
Fauna. Tijdschr. der Nederlandsche Dierkundige Vereeniging,
Deel III., pp. 1-36, Taf. I.-V.

72 Illinois State Laboratory of Natural History.

Imhof, O. E.

'83. Die pelagische Fauna und die Tiefseefauna der zwei Savoyer-
seen : Lac du Bourget und Lac d'Annecy. Zool. An/... VI. Jahrg.,
No. 155, pp. 655-657.

'84. Weitere Mittheilungen iiber die pelagische Fauna der Siiss-
wasserbecken. Zool. Anz., VII. Jahrg., No. 169, pp. 321-327.

'85. Pelagische Thiere aus Siisswasserbecken in Elsass-Lothringen.
Zooi. Anz., VIII. Jahrg., No. 211, pp. 720-723.

'85a. Weitere Mittheiluug iiber die pelagische and Tiefseefauna der
Siisswasserbecken. Zool. Anz., VIII. Jahrg., No. 190, pp. 160-163.

'86. Xeue Besultate iiber die pelagische und Tiefseefauna einiger im
Flussgebiet des Po gelegener Siisswasserbecken. Zool. Anz., IX.
Jahrg. No. 214, pp. 41-47.

'86a. A"oii;iufige Notizen iiber die horizontale und verticale geo-
graphische Verbreitung der pelagischen Fauna der Siisswasser-
becken. Zool. Anz., IX. Jahrg., No. 224, pp. 335-342.

'86b. Uber mikroskopische pelagische Thiere aus der Ostsee. Zool.
Anz., IX. Jahrg., No. 235. pp. 612-015.

'87. Uber die raicroscopische Thierwelt hochalpiner Seen. Zool.
Anz., X. Jahrg., Nos. 241 u. 242, pp. 13-17. 33-42.

'87a. Notizen iiber die pelagische Fauna der Siisswasserbecken.
Zool. Anz., X. Jahrg., Nos. 2G4 u. 265, pp. 577-582, 604-606.

'87b. Studien iiber die Fauna hochalpiner Seen insbesondere des
Kantons Graubiinden. Jahresber. d. naturf. Gesellsch. Graubiin-
dens. N. F., XXX. Jahrg., pp. 45-104.

'88. Die Vertheilung der pelagischen Fauna in den Siisswasser-
becken. Zool. Anz., XI. Jahrg., Xo. 280, pp. 284-291.

'88a. Beitrag zur Kenntniss der Siisswasserfauna der Vogesen.
Zool. Anz., XI. Jahrg.. No. 290, pp. 565, 500.

'90. Notizen iiber die pelagische Thierwelt der Seen in Karnthen
und in der Krain. Zool. Anz., XIII. Jahrg., Nos. 335, 33S, 339. pp.
201-263, 347-349, 372-377.

'90a. Notiz iiber pelagische Thiere aus einem Teiche in Galizien.
Zool. Anz., XIII. Jahrg., No. 336, pp. 2S4-2S5.

'95. Tierwelt der hochalpinen Seen. Biol. Centralbl., Bd. XV., Nr.
13, pp. 507-517.

Joseph, G.
'82. Systematisches Verzeichnis der in den Tropfstein-Grotten von
Krain einheimischen Arthropoden nebst Diagnosen der vom
Verfasser entdeckten und bisher noch nicht beschriebenen Arten.
II. Theil. Erfahrungen im wissenschaftlichen Sammeln und
Beobachten der den Krainer Tropfstein-Grotten eigenen Arthro-
poden. Berl. Entomol. Zeitschr., Bd. XXVI.. Heft 1, pp. 1-50.

North American Fresh-water Cyclopidce. 73

Jurine, L.
'20. Histoire ties Monocles qui se trouveut aux environs de Geneve,
pp. I-XVI. + 1-258, Pis. I -XXII. Geneve et Paris.

Kafka, Josef.
'92. Untersuchuugen liber die Fauna der Gewiisser Bohmens. II.
Die Fauna der Bohmischen Teiche. Archiv d. Naturwissensch.
Landesdurchf. von Bohmen, VIII. Bd., No. II.

Kerville, H. G. de.
'88. Les Crustaces de la Normandie: Especes fluviales, stagnates et
terrestres. Bull, de la Soe. des Amis des Sci. nat. de Kouen, 1888,
l re Sem., pp. 133-158.

Kingsley, J. S.
'84. Entomostraca. Stand. Nat. Hist., Vol. II., pp. 22-41.

Koch, C. L.
'35-'41. Deutschlands Crustaceen, Myriapoden, und Arachniden,
Heft. XXI., XXV. Regensburg.

Kochs, W.
'92. Versuche iiber die kiinstliche Vermehrung kleiner Crustaceen.
Biol. Centralbl., Bd. 12. Xr. 18 u. 19, pp. 599-606; Translation in
Bull. U. S. Fish Cornm., Vol XIV., pp. 306-308.

Ladenburger, R.
'84. Zur Fauna des Mansfelder Sees. Zool. Anz., VII. Jahrg., No.
168, pp. 299-302.

Lande, A
'92. Quelques Remarques sur les Cyclopides. Mem. de la Soc. zool.
de France, T. V., pp. 156-173.

Lauterborn, R.
'94. Uber die Winterfauna einiger Gewiisser der Oberrheinebene.
Mit Beschreibungen neuer Protozoen. Biol. Centralbl., Bd. XIV.,
Xr. 11., pp. 390-398.

Lilljeborg, W.
'53. De Crustaceis ex ordinibus tribus : Cladocera, Ostracoda, et Cope-
poda, in Scania occurrentibus. Pp. I.-XV. -4- 1-122, Pis. I.-XXVI.

Loven, S.
'61. Om nagra i Vettern och Venern funna Crustaceer. Ofv. Kongl.
Vet.-Akad. Forhandl., Arg. XVIII., No. 7, pp. 285-314.

Lubbock, J.
'63. Notes on some New or Little-known Species of Fresh-water
Entomostraca. Trans. Linn. Soc. London, Vol. XXIV., pp. 197-210
PI. XXXI.

74 Illinois State Laboratory of Natural History.

Marsh, C. D.
'91. Preliminary List of Deep-water Crustacea in Green Lake, Wis.,

U. S. A. Zool. Anz., XIV. Jahrg., No. 370, pp. 275, 276.
'92. On the Deep-Water Crustacea of Green Lake. Trans. Wis.

Acad. Sci., Arts, and Letters, Vol. VIII., pp. 211-213.
'93. On the Cyclopidaj and Calanidae of Central Wisconsin. Trans.

Wis. Acad. Sci., Arts, and Letters, Vol. IX.. pp. 189-221, Pis.

III.-VI.
'93a. Notes on the Copepoda of Wisconsin. Science, Vol. XXIL,

No. 544. pp. 3, 4.
'95. On the Cyclopida? and Calanidre of Lake St. Clair, Lake Mich-
igan, and certain of the Inland Lakes of Michigan. Bull. Mich.

Fish Comm., No. 5. 24 pp., 9 Pis.

Milne-Edwards, H.
'34-'40. Histoire naturelle des Crustaces, comprenant l'anatomie,
la physiologic et la classification de ces anirnaux. Tome I., II.,
III. 42 Pis. Paris.

Moniez, R.
'87. Liste des Copepodes, Ostracodes, Cladoctres, et de quelques

autres Crustaces recueillis a Lille en 188G. Bull, de la Soc. zool. de

France. T. XII.. pp. 568-578.
'89. Note sur la faune des eaux douces de la Sicilie. Feuille des

jeunes Naturalistes, Annee 20, No. 230, pp. 17-19.
'89a. Faune des eaux souterraines du Departement du Nord, et en

particulier de la ville de Lille. Kev. Biol, du nord de la France.

l re Ann., pp. 175-179.
'89b. Sur quelques Cladoceres et sur un Ostracode nouveaux du

Lac Titicaca. Rev. Biol, du nord de la France, l re Ann., p. 421.

Mrazek, A. v

'91. O hermafroditismu u Copepodu. Vestnik Krai. Ceske Spol.

Nauk., pp. 389-393, PI. XII.
'93 Pffspevky k poznnai Sladkovodnich Copepodi°i. Vestnik Krai.

Ceske Spol. Nauk. Tfida math.-pf ir., 1893. 74 pp., Pis. VI.-VIII.
'93a. Uber abnorme Vermehrung der Sinneskolben an dera Vorder-

fiihler des Weibchens bei Cyclopiden und die niorphologische

Bedeutungderselben. Zool. Anz., XVI. Jahrg., No. 417, pp. 133-138.
'93b. Uber die Systeraatik der Cyclopiden und die Segmentation

der Antennen. Zool. Anz., XVI. Jahrg., No. 424. pp. 285-289; No.

425, pp. 293-299.
'93c. Zur Morphologie der Antenna der Cyclopiden. Zool. Anz..

X VI. Jahrg.. No. 430. pp. 376-385.

North American Fresh-water CyclopidcB. 75

'95. Copepoden. Deutsch-Ost-Africa Wiss. Forschungsresultate,
etc., Band IV., Die Thierwelt Ost-Afrikas. 11 pp., 3 Pis.

Miiller, O. F.

1792. Entomostraca sen Insecta testacea quae in aquis Daniae et
Norvegiae reperit, descripsit et iconibus illnstravit. 134 pp., 21
Pis. Havniae.

Nordqvist, O.
'86. Bidrag till Kannedomen om Crustacefaunan i nagra af mellersta
Finlands sjoar. Acta Soc. pro Fauna et Flora Fenn., T. III., No. 2.
pp. 1-26.

'87. Die pelagische und Tiefsee-Fauna der grosseren finnischen
Seen. Zool. Anz., X. Jahrg., Nos. 254, 255, pp. 339-345, 358-362.

'90. Bidrag till Kannedomen om Bottniska vikens och norra
Ostersjons evertebratfauna. Meddel. af Soc. pro Fauna et Flora
Fenn., 17 Haft., pp. 83-12S.

Nusbaum, J.
'92. Zur Kenntnis der Wiirmerfauna und Crustaceenfauna Polens.
Biol. Centralbl., Bd. XII., Nr. 2, pp. 54-58.

Pavesi, P.
'79. Nuova serie di ricerche della fauna pelagica nei lagbi italiani.
Rend, del R. Inst. Lombardo, Ser. II., Vol. XII., fasc. XI., XII.
10 pp.
'79a. Ulteriori studj sulla fauna pelagica dei lagbi italiani. Rend,
del R. Inst. Lombardo, Ser. II., Vol. XII., fasc. XVI. 21 pp.

'82. Excursione Zoologica al Lago di Toblino. Atti della Soc. Ital.
di Sci. Nat., Vol. XXV. 5 pp.

'83. Altra serie di ricerche e studi sulla fauna pelagica dei laghi
italiani. Atti della Soc. Ven.-Tren. di Sci. Nat., Vol. VIII., pp.
340-403, Pis. VIII.-XIV.

Poggenpohl, M. J.
'74. Verzeichniss der Copepoden, Cladoceren, und Ostracoden der
Umgebung von Moskau. Schriften der Gesellsch. v. Freunden d.
Naturwissensch., etc., zu Moskau, Bd. X., Abt. II., pp. 69-77, Taf.
XV.-XVII. (German title of Russian article.)

Poppe, S. A.
'84. Bemerkungen zu R. Ladenburger's: Zur "Fauna des Mans-
felder Sees" in No. 168 des Zoologischen Anzeigers. Zool. Anz..
VII. Jahrg., No. 175, pp. 499, 500.

'89. Xotizen zur Fauna der Stisswasser-Becken des nordwestlichen
Deutschland mit besonderer Beriicksichtiguug der Crustaceen.
Abh. d. Naturw. Ver. zu Bremen, Bd. X., pp. 517-550, Taf. VIII.

76 Illinois State Laboratory of Natural History.

'89a. Berichtigung zu Dr. O. E. linhol's Aufsatz: " Fauna tier Siiss-
wasserbecken " in Xo. 275 des Zool. Anz. 1888, p. 106. Zool. Anz.,
XII. Jahrg., Xo. 300. pp. 99, 100.

'91. Beitrage zur Fauna der Insel Spiekerooge. Abh. d. Xaturw.
Ver. zu Bremen, Bd. XII. 6 pp.

Poppe, S. A., u. Mrazek, A.
'95. Entomostraken des Xaturhistorischen Museums in Hamburg.
Jahrb. der Hamburgischen Wiss. Anstalten, XII.. Beiheft. 20 pp.,
4 Pis.

Poppe, S. A., et Richard, J.
'90. Xote sur divers Entomostraces du Japon et de la Chine.
Bull, de la Soc. zool. de France, T. XV., pp. 73-78.

Rath, O. v.
'91. Zur Kenntniss der Hautsinnesorgane der Crustaceen. Zool.
Anz., XIV. Jahrg., Nos. 365, 366, pp. 195-200, 205-214.

Rehberg, H.
'80. Zwei neue Crustaceen aus einem Brunnen auf Helgoland. Zool.
Anz., III. Jahrg., Xo. 58, pp. 301-303.

'80a. Beitrag zur Kenntniss der freilebenden Siisswasser-Copepoden.
Abh. d. Xaturw. Ver. zu Bremen, Bd. VI., pp. 533-554, Taf. VI.

'80b. Weitere Bemerkung uber die freilebenden Siisswasser-Copep-
oden. Abh. d. Xaturw. Ver. zu Bremen, Bd. VII., pp. 61-67, Taf. IV.

Richard, J.
'87. Liste des Cladoceres et des Copepodes d'eau douce observes en

France. Bull, de la Soc. zool. de France. T. XII., pp. 156-163.
'88. Cladoeeres et Copepodes non marins de la Faune francaise.

Rev. Sci. du Bourbonnais. mars-avril, 18S8, pp. 1-28
'90. Sur les Entomostraces et quelques autres animaux inferieurs

des lacs de TAuvergne. Bev. des Sci. Nat. Appliquees. Xo. 10. 20

mai, 1890.
'90a. Sur la glande du test des Copepodes d'eau douce. Xote pie-

liminaire. Bull, de la Soc. zool. de France, T. XV., pp. 113-118.
'90b. Description du Bradya Edwardsi. < opepode.aveugle nouveau,

vivant an Bois de Boulogne avec divers Entomostraces dans les

eaux alimentees par le puits artesien de Passy. Mem. de la Soc.

zool. de France, T. III., pp. 214-222.
'90c. Entomostraces d'eau douce recueillis a Belle He (Morbihan).

Bull, de la Soc. zool. de France, T. XV., pp. 33, 34.
'91. Sur les Entomostraces du Lac Balaton. Bull, de la Soc. zool.de

France, T. XVI., pp. 135-137.
'91a. Entomostraces d'eau douce de Sumatra et de Celebes. Zool.

Ergeb.einerReiseinXiederland.Cv-t-Ind., Bd. II., pp. 118-134, PI. X.

North American Fresh-water Cyclopidce. 77

'91b. Recherehes sur le Systeme glandulaire et sur le Systeme
nerveux des Copepodes libres d'eau douce. Ann. Sei. Xat., Zool.,
T. XVI., pp. 113-270, PJs. V.-VIII.

'92. Sur quelques Entomostraees de Pile d'Elbe et de 1'ile de Monte-
Cristo. Bull, de la Soc, zool. de France, T. XVII., pp. 226-229.

'93. Copepodes recueillis par M. le Dr. Theod. Barrois en Egypte,
en Syrie, et en Palestine. Rev. Biol, du nord de la France, 5 e aim.,
Xo. 10, juillet, 1893. 36 pp., 51 Fig.

'94. Sur quelques aniraaux inferieurs des eaux douees du Tonkin
(Protozoaires, Roti feres, Entomostraees). Mem. de la Soc. zool. de
France, T. VII., pp. 237-243.

'94a. Entomostraces recueillis par M. E. Modigliani dans le Lac
Toba (Sumatra). Ann. del Mus. Civ. di Storia Natural e di Genova,
Serie 2. a, XIV. (XXXIV.). pp. 565-578.

'95. Sur quelques Entomostraces d'eau douce d'Hai'ti. Mem. de la
Soc. zool. de France, T. VIII. 11 pp. 11 figs.

'95a. Cladoeeres et Copepodes recueillis par M. Kavraisky pres de
Tillis et dans le Eac Goktsha. Bull, de la Soc. zool. de France. T.
XX.. pp. 91,92.

'95b. Contribution a la Faune des Eutornostraces de la France.
Feuille des jeunes Naturalistes, III. Serie, 25 e Ann., Nos. 295 et
296. 9 pp.

Riickert, J.
'95. Zur Befruehtung von Cyclops strenuus (Fisch.). An at. Anz., X.
Bd., Xo. 22, pp. 708-725; Abstract, Zool. Centralbl., II. Jahrg., pp.
555. 556.

'95a. Uber das Selbstandigbleiben der vaterliehen und miitter-
licben Kernsubstanz wahrend der ersten Entwicklung des befrueh-
teten Cyclops-Eies. Arcb. f. Mikr. Anat.. Vol. 45, pp. 339-369. Taf.
XXI., XXII.; Abstract, Zool. Centralbl., II. Jahrg., pp. 554, 555.

Sars, G. 0.
'62. Oversigt af de indenlandske Ferskvandscopepoder. Forhandl.
Vidensk.-Selsk. i Christiania, 1862, pp. 212-262.

'63. Beretning om en i Sommeren 1S62 foretagen zoologisk Reise i
Christianias og Trondbjems Stifter. Xyt Mag. f. Xaturvidensk.,
Bd. XII., pp. 193-252.

'64. Beretning om en i Sommeren 1S63 foretagen zoologisk Reise i
Christianias Stifter. Nyt Mag. f. Naturvidensk., Bd. XIII. 36 pp.

'89. On a small Collection of Fresh-water Entomostraca from Syd-
ney. Christiania Vidensk.-Selsk. Forhandl., 1889, No. 9, pp. 1-9.

'96. On Fresh-Water Entomostraca from the Neighborhood of
Sydney partly raised from dried Mud. 81 pp., 8 PJs. Kristiania.

78 Illinois State Laboratory of Natnial History.

Say, T.
'18. An Account of the Crustacea of the United States. Journ.
Acad. Nat. Sci. Phil., Vol. I., pp. 421-458.

Schmankewitsch, W.
'77. Zur Kenntniss des Einflusses der ausseren Lebensbedingungen
auf die Organisation der Thiere. Zeitschr. f. wiss. Zool.. Bd.
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Schmeil, O.
'91. Beitriige zur Kenntniss der Siisswasser-Copepoden Deutsch-
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'92. Deutschlands freilebende Siisswasser-Copepoden. I. Teil. Bib-
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'94. Zur Hohlenfauna des Karstes. Zeitschr. f. Xaturwiss. Halle.
Bd. 06, pp. 339-353.

Scott, T.
'94. On the food of Utricularia vulgaris, an Insectivorous Plant.
Ann. Scot. Xat. Hist,, Xo. 10. pp. 105-112.
Scourfield, D. J.
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'94. Entomostraca and the Surface-film of Water. Journ. Linn. Soc.
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'95. A Preliminary Account of the Entomostraca of Xorth Wales.
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'91. Materiaux pour servir a l'etude des Crustaces d'eaux douces

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North American Fresh-water Cyclopidce. 79

Turner, C. H.
'92. Notes upon the Cladocera, Copepoda, Ostracoda, and Eotifera
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Vernet, H.
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Voeltzkow, A.
'91. Vorlauriger Bericht iiber die Ergebuisse einer Untersuchung
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Vosseler, J.
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1886, pp. 167-202, Taf. IV.-VI.

'89. Die Copepodenfauna der Eifelmaare, [including (p. 123)], "Uber
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'91. Die Krebsfauna unserer Gewiisser. In Zacharias's '"Die Tier- u.
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'82, Materyaly do fanny jezior tatrzanskich. Copepoda. Sprawozd.
Kom. fiz. Akad. uiniej. T. XVI. 25 pp., 2 Pis.

80 Illinois State Laboratory of Natural History.

'92. Skorupiaki i Wrotki (Rotatoria) slodkowodne zebrane w
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Zacliarias, O.
'85. Ergebnisse einer zoologiscbeu Exkursion in das Glatzer-.Iser-,

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deutscher Seen. Zeitscbr. f. wiss. Zool., Bd. XLV.. pp. 255-2S1.

Taf. I.
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'87b. Faunistiscbe Studien in westpreussicben Seen. Schrift. der

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VIII.. Xo. 17. pp. 540.541.
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11 u. 12 pp. 377-4S4.

'94. Uber die Verteilung der Flanktonorganismen innerhalb eines
Sees. Biol. Centralbl., Bd. XIV., Xr. 3, pp. T22-12S.

'95. Uber die vertikale Verteilung limnetiscber Crustaceeu, insbe-
sondere iiber diejenige von Cyclops oithonoides. Biol. Centralbl.,
Bd. XV.. Xr. 18, pp. 6S6-688.

Zaddach, E. G.
'44. Synopseos Crustaeeorum Prussicorum Prodromus. pp. I -VIII.
-\- 1-33. Regiomonti (Konigsberg).

Zenker, W.
'54. Uber die Cyclopiden des siissen Wassers. Archiv fiir Xatur-
gesch.. XX. .Tabrg., Bd. 1, pp. S8-103, Taf. VI.. Fig. 8-14.

Zschokke, F.
'90. Faunistiscbe Studien an Gebirgsseen. Verbal. Naturf. Gesellseh.
in Basel. Bd. IX. 62 pp.

'90a. Beitrag zur Kenntnis der Fauna der Gebirgsseen. Zool.
Anz .XIII. Jabrg., Xo. 326, pp. 37-40.

Nortli American Fresh-water Cyclop idee. 81

'91. Weiterer Beitrag znr Kenntnis tier Fauna von Gebirgsseen.
Zool. Anz., XIY. Jahrg., Nos. 360 n. 361, pp. 119-123 u. 126-129.

'94. Die Tierwelt tier Juraseen. Rev. Suisse tie Zool., T. II., pp.
349-376, PI. XIV.

'95. Die Fauna hochgelegener Gebirgsseen. Yerhandlung der
Naturf. Gesellsch. in Basel. Btl. XI., Heft I., pp. 36-133, Taf. I.

EXPLANATION OF PLATES.

Plate VIII.

Fig. 1. Cyclops leuckarti Clans.

Fig. 2. Last two segments of antenna of same.

Fi<;. 3. Fifth foot of same.

Plate IX.

Fig. 1. Cyclops edax Forbes.

Fit;. 2. Last two segments of antenna of same.

Fig. 3. Fifth foot of same.

Plate X.

Fig. 1. Cyclops viridis Jnrine.

Fit;. 2. Fifth foot of same.

Fig. 3. Reeeptacnlum seminis of same.

Plate XL

Fig. 1. Variations in outer terminal spine of stylet of Cyclops viridis

var. hrevispinosus Herrick.
Fig. 2. Fifth foot of same.

Fig. 3. Keceptaculum seminis of Cyclops viridis var. insectus Forbes.
Fn;. 4 and 5. Fifth foot of same.
Fig. 6. Swimming foot of same.

Plate XII.

Fig. 1. Cyclops bicuspidatus Clans.

Fig. 2. Stylet of same.

Fig. 3. Fifth foot of same.

Fig. 4. Receptaculum seminis of same.

Plate XIII.
Cyclops albidus Jurine.

Plate XIV.
Cyclops ater Herrick.

82 Illinois State Laboratory of Natural History.

Plate XV.

Y\(.. 1. Last two segments of antenna of Cyclops ater Herriek.

Fit;. 2. Fifth foot of same.

Ftg. 3. Receptaculum seminis of same.

Fur. 4. Cyclops modestus Herriek.

Plate XVI.

Fig. 1. Antenna of Cyclops modestus Herriek.

Fig. 2. Fifth foot of same.

Fig. 3. Receptaculum seminis of same.

Plate XVII.

Cyclops

serrulatus Fischer.

Plate XVIII.

Fig. 1.

Cyclops serrulatus Fischer.

Fig. 2.

Fifth foot of same.

Fig. 3.

Receptaculum seminis of same.

Plate XIX.

Fig. 1.

Cyclops prasinus Fischer.

Fig. 2.

Antenna of same.

Plate XX.

Fig. 1. Fifth foot of Cyclops prasinus Fischer.
Fig. 2. Receptaculum seminis of same.
Fig. 3. Cyclops phaleratus Koch.

INDEX.

(Synonyms in Italics.)

Canthoeamptus. 62.
Claeocera, 62.
Copepoda, 27.
Cyclopidje. European, 29.

list of North American species,
63.
Cyclops, 31,63.

afflnis, 29, 65.

agilis, 29.

albidus, 29, 47, 62, 63, 64.

americanus, 37, 38, 42.

annulatus, 33, 35.

ater, 29, 49, 62, 64.

bicolor, 29, 62. 63, 64.

bicuspiclatus, 29, 30, 44, 53, 62,
63, 64.

bisetosus, 29.

brevispinosus, 39, 41.

capilliferus, 51.

crassicaudis, 29.

dybowskii, 29, 62, 63.

edax, 33. 62, 63.

fitnbriatus, 29.

var. poppei, 63, 65.

fluviatilis, 57.

forbesi, 44, 45.

fuseus, 29, 64.

general distribution of. in
North America, 62.

gigas, 29, 37.

gyrinus, 47, 48.

helgolandicus, 29.

hyalinus, 29.

ingens, 37.

insectus, 37,38, 39, 41.

insignis. 29, 63.

lacustris, 29.

leeuwenhoekii, 34, 35.

leuckarti, 29, 31, 34, 36, 63.

leuckarti, 33.

lev is. 37.

macrurus, 29.

Cyclops — continued,
magnoctavus, 57.
minnilus, 44, 45.
modestus, 29, 62, 63, 64.
nanus, 29.
navus, 44, 45.
oithonoides. 29. 63.
parens, 38, 41, 42.
pentagonus, 57.
peramatus, 59, 60.
phaleratus, 29, 30, 59, 63, 65.
prasinus, 57, 63, 65.
pulchellus, 29, 44.
robustus, 29.
scutifer, 29.
serratus, 44, 45.

serrulatus, 29, 30, 54, 62, 63, 65.
var. ele/jans. 54.
var. montanus, 54, 55.
sigriatus, 29.

var. tenuicornis, 47.
strenuus, 29.
thomasi. 44, 45.
unianguiatns, 39, 41.
varicans, 29, 63, 64.
vernalis, 29, 64.
viridis, 29, 30,37, 41,42, 43,
48, 62, 63, 64.
var. brevispinosus, 30, 39,

41, 62, 63, 64.
var. insectus, 31, 41, 62,
63, 64.
Diaptomus, 62.
Eucyclops, 54, 65.
Ilomocyclops, 29. 49, 64.
Macrocyclops, 47, 64.
Microcy clops, 64.
Monoculus quadricornis var. albidus,
47.
var. viridis, 37.
Orthocy clops, 29, 51,64.
Paracyclops, 59, 65.

Plate VIII.

Q

ffl

Pv

Plate IX.

Plate X.

Plate XL

Plate XII.

Plate XIII.

Plate XIV.

Plate XV.

Plate XVI.

Plate XVII.

Plate XVIII.

Plate XIX.

Plate XX.

ERRATA.

Page 31, line 8, for solid read dotted; line 10, for dotted read solid.

Page 34, line 6, for eqwd read subequal.

Page 44, line 8, for species read variety.

Pase 63, line 10, before America insert North.

Page 6(5, under Birge, E. A., for '94 read '95.

Page 73, under Koch, C. L., for XXV. read XXXV.

Page 77, line 2, before Zoology insert 7 e Ser.; line 3, for XVI. read XII.

Page 78, line 13, for Heft II. read Heft 11.

Page 79, for Villipoix, R. M. de, read Villepoir, R. M. de.

Page SO, under Zacharias, O., for '85 read '80; and in entry for 'a7, for
Taf. I. readTaf. XV.

Page SI. line 5. for '95 read '94.

BULLETIN

OF THE

[llinois 3 tate Laboratory

OK

NATURAL HISTORY,

Urbana, Illinois

VOLUME V.

ARTICLE III.— THE NORTH AMERICAN SPECIES OF

DIAPTOMUS.

By FREDERICK WILLIAM SCHACHT, B. S.

Illinois State Laboratory of Natural History,
URBANA, ILLINOIS,

1897.

State Laboratory of Natural History.

LABORATORY STAFF.

Professor Stephen Alfred Forbes, Ph. I).,
Director of State Laboratory and State Entomologist.

Charles Arthur Hart,
Systematir Entomologist and Curator of Collections.

Frank Smith, A. M.,

Assistant Zoologist.

Charles Atvvood Kofoid, Ph. D.,

Zoologist, awl Superintendent of Biological Station.

Charles Christopher Adams, B. S.

Entomological Assistant.

Ralph Waldo Brauciier, B. S..

Entomological Assistant.

Mary Jane Snyder.

Secretary.

Henry Clinton Forbes,
I!)isi7iess Agent and Librarian.

Lydia Moore Hart,
Artist.

Article III. — The North American Sj>ccies of Diaptomus.

By Frederick William Schacht.

INTRODUCTION.

The first published reference to that group of genera of
Entomostraca now known under the family name of Centro-
pagidce is contained in 0. F. Muller's "Entomostraca seu
Insecta testacea quae in aquis Daniae et Norvegiae reperit,"
etc., published at Frankfort-on-the-Main in 1785, in which

The following paper was prepared in the course of
undergraduate study in the Zoological Department of the
University of Illinois, and was accepted by the Faculty
of the University June 7, 1897, as a thesis for the degree
of Bachelor of Science in Zoology.

187 7 ana tnose oi marsii in iodi. » »niyjc a^x^i^a v ^.
kentuckyensis) named by Chambers in 1881 is so imperfectly
described that its recognition is apparently impossible. Since
the publication of Underwood's " List of the described Species
of Fresh- water Crustacea from America North of Mexico"
('86) the number of recognized North American species of
Diaptomus has increased from five to twenty-three.

The literature of the genus previous to 1889 was widely
scattered and the synonymy greatly complicated, but the
comprehensive and careful "Revision" published in that
year by de Guerne and Richard ('89b) has had the effect
greatly to facilitate its study. The most important recent
European contributions to a knowledge of the Centropagidce

9?

State Laboratory of Natural History.

LABORATORY STAFF.

Professor Stephen Alfred Forbes, Ph. D.,

Director of State Laboratory and State Entomologist.

Charles Arthur Hart,

£j>iwmo logical jissisiam.

Mary Jane Snyder,

Secretary.

Henry Clinton Forbes,
Business Agent and Librarian.

Lydia Moork Hart,
Artist.

Article III. — The North American Sp)ccies of Diaptomus.
By Frederick William Schacht.

INTRODUCTION.

The first published reference to that group of genera of
Entomostraca now known under the family name of Centro-
pagidee is contained in 0. F. Midler's "Entomostraca seu
Insecta testacea quae in aquis Daniae et Norvegiae reperit,"
etc., published at Frankfort-on-the-Main in 1785, in which
paper certain copepod species now included under the genus
Diaptomus were treated under the general name of Cyclops.
Species of Diaptomus were later described by Jurine ('20)
under Monoculus, but the genus Diaptomus was first estab-
lished by Westwood ('36). Various names have since been
applied more or less closely to the generic group : Cyclopsina,
Milne-Edwards ('38); Qlaucea, Koch ('38); and Cyclops,
Nicolet ('48).

The first American species of Diaptomus recognizably
described was D. sanguineus Forbes ('76). Later Dr. Forbes
( '82a) described three additional species of this genus (sicilis,
leptopus, and stagnalis), and two new genera of Centropagidce
(Epischura and Osphranticum), with a single species of each.
Prof. C. L. Herrick's publications on the group began in
1877 and those of Marsh in 1891. A single species (D.
kentuckyensis) named by Chambers in 1881 is so imperfectly
described that its recognition is apparently impossible. Since
the publication of Underwood's " List of the described Species
of Fresh-water Crustacea from America North of Mexico"
('86) the number of recognized North American species of
Diaptomus has increased from five to twenty-three.

The literature of the genus previous to 1889 was widely
scattered and the synonymy greatly complicated, but the
comprehensive and careful "Kevision" published in that
year by de Guerne and Richard ('89b) has had the effect
greatly to facilitate its study. The most important recent
European contributions to a knowledge of the Centropagidce

97

98 Illinois state Laboratory of Natural History. .

have been made by Claus, Schmeil, Poppe, Imhof, Zacliarias,
and others, in Germany ; by Brady, in England ; by Nord-
qvist, in Finland; by Bars, in Norway; and by Lilljeborg in
Sweden, the latter especially having described a number of
American species. Perhaps the finest work yet published
on Copepoda in general is Giesbrecht's monograph on the
" Pelagischen Copepoden des Golfs von Neapel" ('92), the
general classification of which is followed in the present
article.

It has been my purpose in preparing this paper to do for
the students of American Centropagidce a service similar to
that which de Guerne and Richard have rendered to students
of this group as distributed throughout the world. I am
under especial obligation to my instructor, Prof. S. A. Forbes,
to whose encouragement and aid any value this paper may
have is to be largely attributed. I am indebted also for
specimens or other favors to Dr. Wilhelm Lilljeborg, of
Upsala, Sweden ; to Dr. Otto Schmeil, of Magdeburg, Ger-
many; to Herr S. A. Poppe, of Vegesack, Germany; to Prof.
C. Dwight Marsh, of Ripon College, "Wisconsin ; to Prof. L.
S. Ross, of Drake University, Des Moines, Iowa; to Mr.
Adolph Hempel, now of the Museu Paulista, Sao Paulo, Bra-
zil ; to Prof. Frank Smith, of the University of Illinois ; to Mr.

C. E. Phillips, of Millington, 111. ; and to my friend and fellow
student, Mr. E. B. Forbes. I have also to call attention to
the fact that most of the figures accompanying this paper
were drawn by the Artist of the State Laboratory, Miss
Lydia M. Hart.

From Dr. Lilljeborg I received specimens of Diaptomus
signicauda, D. minutus, 1>. trybomi, D. eiseni, I). francisca-
nus, Epischura nevadensis, and K. nordenskibldi. Prof. Ross
and Mr. Hempel kindly loaned me their personal collections,
the former thus furnishing me D. siciloides, I >. piscina, and

D. clavipes sp. nov., and the latter, D. mississippiensis and
D. albuquerquensis. Prof. Marsh has sent me slides or entire
specimens of D. ashlandi, 1 >. mississippiensis, and D. reighardi.
To Dr. Schmeil I owe thanks for several kind letters, for the
European species 1>. gracilis, I>. graciloides, I>. castor, D.

North American Species of Diaptomus. 99

salinus, D. coeruleus, and D. zachariasi, and for specimens
of Heterocope and Temorella, — all of which, however, arrived
too late to be of service to me in connection with this paper.
From Herr Poppe I received the following species : D. tyrrelli,
D. gibber, D. incongruens, D. deitersi, D. drieschi, D. zacha-
riasi, and Limnocalanus sinensis.

The material at my command was nearly complete, includ-
ing all but two of the known North American forms (D.
novamexicanus and D. birgei), and the collection of the liter-
ature of the group to which I have had access is probably as
ample as that to be found in any library in this country.
In compiling the bibliographical list appended to this paper,
Schmeil's monograph on the Ccntropag'uhe ('96) was taken
as a basis and was especially helpful, while a great deal was
also gained from the works of de Guerne and Eichard.

By far the greater part of the collections examined are the
property of the Illinois State Laboratory of Natural History.
They represent localities distributed over the entire continent,
from Massachusetts in the East to Oregon in the West, as far
south as Florida and as far north as Canada, and including the
following states : Massachusetts, Florida, Mississippi, Ohio,
Indiana, Illinois, Iowa, Minnesota, Michigan, Wisconsin,
Oregon, Washington, Montana, Wyoming, California, Idaho,
and Nevada. In addition to the above I have examined
specimens from Manitoba, Newfoundland, and Greenland.

The localities represented by these collections vary widely
in character, ranging from temporary pools on the Illinois
prairies to Lakes Michigan and Superior; from the warm
lakes of the Florida swamps to the cold mountain lakes of
the Eockies ; and from the small head-water streams of the
Kaskaskia to the sluggish Illinois and the mighty Mississippi.
The collections were made at all seasons of the year and at
nearly all times of the day and night.

Although no very complete data for any single locality are at
hand, it is found that in ordinary years the spring and early
summer are the most favorable seasons for collecting in our
latitudes. Individuals are found, however, at all times ; and
in some cases the normal habitat is a lake whose waters are

100 Illinois State Laboratory of Natural History.

but little above the freezing point, or even, as in the case of
J>. minutus, water flowing from the foot of a glacier- Although
this would seem to indicate that these crustaceans are quite
hardy, I have repeatedly found that in jars containing living
specimens of Cyclops, Diaptomus, and Osphranticum, those
of Diaptomus were the first to succumb to unfavorable con-
ditions.

The genus Diaptomus is the most cosmopolitan of its
family, species having been reported from North and South
America, Europe, Asia, Africa, and Australia. No species,
however, is known to be common to the mainlands of Europe
and of America. This fact is the more remarkable since
almost the direct opposite is true of the companion genus,
( 'yclops, only one or two species of which are, so far as known,
peculiar to this continent. Even 1>. minutus, which is found
in Oregon, Illinois, Wisconsin, Minnesota, Michigan, New-
foundland, Greenland, and Iceland, has not as yet been found
in northern Europe or even in Great Britain, although the
expanse of salt water between Iceland and Scotland or be-
tween Iceland and Scandinavia is but little greater than that
between Greenland and the mainland of North America. But
few species of this genus have been described from tropica)
regions, most of them having thus far been found in the north
temperate zone ; a fact to be attributed doubtless in large
measure to the greater attention paid to zoological studies in
these northern latitudes.

In this paper the plan followed by de Guerne and Richard
in their "Revision" has been adopted, separate keys being
made for males and for females. When females are so nearly
alike as in 1>. sicilis, siciloides, pallidus, and ashlandi, it ig
somewhat difficult to find distinguishing characters, and
differences not usually taken into account must be seized
upon. The males are much more easily separated, since they
offer a larger number of peculiarities. Giesbrecht and
Schrneil have paid considerable attention to the armature of
the entire male prehensile antenna instead of regarding only
that of the last three segments, and in one or two cases I
have done the same. In this connection a fact became

North American Species of Diaptomus. 101

evident which if found to be generally true will necessitate a
slight modification of the description of the family Centro-
pagidce. I refer to the presence of a sense-club on the first
segment of the right male antenna. In his monograph
Giesbrecht in his description ('92, p. 85), says, "Vordere
antennen almlich wie bei den Calaniden gebaut." On another
page (42) we find this statement: "The normal number of
processes seems to be three for each segment, a proximal
seta, a distal seta, and a sensory structure [asthetask], but
this triad is never complete on all segments, the sense-club
on the first segment being always wanting and the sense-club
and proximal seta nearly always absent on the twentieth to
the twenty-fourth." In Diaj)tomus stagnalis and D. clavipes
a sense-club is present on the first segment. The statement
that the inner rami of the fifth pair of feet are "rudimentary,
one-segmented, or lacking" will not hold in many species.
Taking only those forms among non-American species which
were described in de Guerne and Richard ('89b), we find the
following with fat'o-segmented inner rami : D. minis, D.
lobatus, D. thceli, and D. glacialis, Lilljeborg; D. ccrruleus
Fischer, D. gibber Poppe, and D. wierzejskii Richard ; and
at least three American species have the inner ramus two-
segmented — D. stagnalis Forbes distinctly, and T). eiseni
Lillj. and D. albuquerquensis Herrick indistinctly so.

It is expected that the keys here printed will be used in con-
nection with the descriptions and figures, since the species
vary within certain limits, and no hard and fast description
can be given which will cover the peculiarities of every indi-
vidual of a species. Local varietal differences or slight vari-
ations in proportion may make a key useless, and in all
cases the totality of characters should be considered. A
glance at the figures will indeed often be found more helpful
than any verbal description.

Following the usual plan of specific descriptions, the first
paragraph, referring to the general appearance of the body,
thorax, abdomen, and furca and their relative proportions,
applies always to the female unless especially stated other-
wise.

102 Illinois State Laboratory of Natural History.

SYNOPSIS OF THE RELATIONSHIPS OF THE GENERA Os]>h f(l liticiim,

Limnocalanus, Diaptomus, and Epischwra,
of the family C entropagidce .

(Adapted and compiled from Giesbrecht ('92), and from manuscript
of Prof. S. A. Forbes.)

1 (19). Division of body into cephalothorax and abdomen

between the thoracic segment bearing the fifth pair
of feet and the segment bearing the genital apertures.
In the male the fifth pair of feet assists in copulation.
Abdomen with five segments ; without appendages.
Genital organs of the male unsymmetrical. Pulsating
dorsal vessel generally present. Female deposits eggs
singly or carries them with her in single sac until emer-
gence of the nauplii. Suborder I. GYMNOPLEA.

2 (3). Anterior antennae of male symmetrical or nearly so,

and more richly provided with sense-clubs [cesthctasks]
than those of the female. Fifth pair of feet of female
either normal, or degenerate to complete disappear-
ance. Secondary sexual distinctions of male not con-
fined to peculiarities in the structure of the body, the
antennae, the fifth pair of feet, and the segmentation of
the abdomen, but usually present in the cephalic
appendages and sometimes also in the swimming feet.
Marine. Tribe I. Amphaskandria.

3 (2). Anterior antennae of male unsymmetrical. Fifth pair

of feet in the female either normal or degenerated, but
never absent. Secondary sexual characters of male
generally confined to peculiarities in the structure of the
body, the antennae, and the fifth pair of feet. Marine
and fresh- water. Tribe II. Heterarthrandria.

4 (18). Eostrum present. Fourth and fifth thoracic seg-

ments confluent.
5(6). Abdomen of female 1-3-segmented. Antennae 16-24-
jointed ; last two segments always confluent. In the
male the fifth pair of feet rarely with a rudimentary
inner ramus. Antenna 1 with segments 19-21 and
sometimes 22-25 confluent. Marine.

Family Pontellid^:.

North American Species of Diaptomus. 103

6(5). Abdomen of female 3- or 4-segmented ; sometimes
unsymmetrical. Antennae never with less than 24 seg-
ments. In the male, segments 19-21 and generally 22
and 23 are confluent. Abdomen 5-jointed ; either right
or left antenna prehensile. The fifth pair of feet are
grasping organs and both always present, but with
inner ramus normal, or degenerate to complete dis-
appearance. Family Centropagims.

7 (8). Thorax 6-jointed. All the feet of female with 3-seg-

mented rami. Abdomen 3-jointed. Antenme 25-
jointed, segments 24 and 25 confluent. Eight male
antenna prehensile. Outer ramus of left fifth foot
2-jointed ; of right, subchelate.

Subfamily Centeopagina.

8 (7). Thorax 5-jointed. Fourth and fifth thoracic seg-

ments confluent.

9 (16,17.) Abdomen of female 3-jointed, sometimes unsym-

metrical. Antennae 23- or 24-jointed. Four anterior
pairs of feet generally with 3 -segmented rami. Fifth
pair of feet degenerate, with inner ramus wanting or
small and 1-jointed, outer ramus 1-3 jointed. Pre-
hensile antenna generally the right; segments 19-21
and 22 and 23 confluent. Subfamily Temorina.

10 (11). Furca with but three large terminal setae to each

ramus. Abdomen of male unsymmetrical, provided
with lateral prehensile apparatus. Fifth pair of legs
of female uniramose, 3-jointed, not terminating with
a long spine. Genus Epischura.

11 (10). Furca with four large terminal setae to each ramus.

12 (13). Inner ramus of first pair of legs 2-jointed; of the

following three pairs 3-jointed. Fifth pair of legs in
both male and female biramose, inner ramus rudi-
mentary. Genus Diaptomus.

13 (12). Both inner and outer rami of the first four pairs of

legs 3-jointed. Fifth pair of legs in both sexes biramose,
those of the female differing from the other legs only
by the presence of a strong inner hook on the second

104 Illinois State Laboratory of Natwral History.

joint of the outer ramus ; those of the male with the
inner ramus 3- jointed and provided with plumose
hairs, as in the other legs.

14 (15). Fifth pair of legs of female with the inner hairs of the

last joint of the outer ramus transformed into short
thick spines. In the male, outer ramus of left leg of
fifth pair with two joints ; outer ramus of right leg with
three. Genus Osphranticum.

15 (14). Fifth pair of legs of female with the inner hairs of

the last joint of the outer ramus long and plumose.
Fifth pair of legs of male with both outer rami 2- jointed.

Genus Limnocalanus.

16 (9, 17). Abdomen of female 4-jointed, symmetrical.

Antennas 25-jointed, articles 24 and 25 not confluent.
Four anterior pairs of feet generally with 3-segmented
rami, the fifth with 3-segmented outer and 2- or 3-seg-
mented inner ramus. Male antenme with segments
19-21 and 21-23 confluent. Fifth pair of feet sub-
chelate ; the right with 2-, the left with 3-segmented
rami. Subfamily Leuckartiixa.

17 (9,16). Abdomen 3- or 4-jointed, not always symmetrical.

Four anterior pairs of feet with 3-jointed rami. Gen-
erally the left antenna of the male geniculate. Articles
19-21, 22 and 23 (or 22-25), and 1 and 2 confluent.
Fifth pair of legs with 3-segmented outer and 1-3-
segmented inner rami. ChelaB undeveloped or want-
ing. Subfamily Heteroch.etixa.

18 (4). Rostrum wanting. Fourth and fifth thoracic segments

of female not confluent. Abdomen 3-segmented. Male
genital opening on the left ; right antenna prehensile,
segments 17 and 18, and 19 and 20 confluent. Inner
rami of fifth pair of feet wanting; outer ramus of left
foot 4-segmented, of right foot 3-segmented. Marine.

Family C'axdacid.e.

19 (1). Division of body into anterior and posterior parts in

front of the last (fifth) thoracic segment. This bears,
almost without exception, a more or less rudimentary

North American Species of Diaptomus. 105

pair of feet, which in the male never assist in
copulation ; on the contrary, the male attaches the
spermatophores directly to the vulva of the female
without the help of appendages. Genital organs of
the male generally paired, the openings always sym-
metrical. Pulsating dorsal vessel almost always
absent. The female carries the eggs w T ith her, gener-
ally cemented into one or two egg sacs, until emer-
gence of the young.

Suborder II. PODOPLEA.

Diaptomus Westwood.

Cyclops, O. F. Miiller, 17S5.
Monoculus, Jurine, *20.
Diaptomus, Westwood, '36.
Cyclopsina, Milne-Edwards. ";58.
Glaucea, Koch, 'So- 41
Cyclops, Xicolet, '48-49.

" Cephalothorax always with seven segments, of which the
anterior two, indistinctly confluent, form the head. The last
thoracic segment in the female rather large, posteriorly deeply
emarginate in the middle, and often produced laterally on
both sides into a biangulate lamina. Abdomen short, nar-
rower than the thorax ; in female of four segments (caudal
rami included), of which the first is dilated anteriorly and
very often armed with a lateral spine on each side ; in male
composed of six obvious segments of about equal width.
Caudal rami with five uniarticulate plumose setae and with
another much smaller, more slender seta within. The front
provided with two minute tentaculiform appendages. The
first pair of antennas composed of 25 segments, increasing
slightly in length toward the tip. The geniculate articulation
between the 18th and 19th segments of the right male
antenna ; the six preceding segments swollen, the five following
sometimes confluent into two articles. The outer ramus of
the second pair of antennas 7 -jointed, longer than the inner
ramus, the last article longest of all and armed with very
long apical seta? ; setse of preceding articles short and

106 Illinois State Laboratory of Natwral History.

subequal. Second pair of maxillae short and thick ; third
pair elongate, directed forward, 7 -segmented, and provided
with short setae. The eight anterior swimming feet biramose,
the inner ramus of the first pair 2-, of the following pairs 3-seg-
mented. The last pair of feet different from the rest, 5-seg-
mented, the second segment armed within with a small
appendage or rudiment of an inner ramus ; in the female
short, equal, the last segment very short and rudimentary,
the penultimate always produced into a strong hook curved
inward ; in the male the right foot subchelate, the last article
formed into a very long movable hook. Eye single."*

The following remarks on the genus are from de Guerne
and Kichard's "Revision " :

"The genus Diaptomus, known at a very early date, was
for a long time confounded with Cyclops. Clearly distin-
guished much later, it contained for a very long time only a
few recognized species, and even these were insufficiently
denned. Since their study has been taken up with more
attention other forms have been distinguished, and the num-
ber of species now exceeds forty, and further explorations will
undoubtedly bring others to light.!

" If we attempt to arrange characters in the order of their
importance from a systematic point of view, we must say
in the beginning that they are furnished almost wholly by
the males. Except in certain cases the isolated females are
difficult to determine. They are, however, rarely met with
alone, and collections commonly contain, whatever the season,
both sexes together.

" Among the characters furnished by the male, the greatest
importance must be assigned to those of the fifth pair of feet.
The length of the inner rami, composed of one or two seg-
ments, varies considerably (minutus to castor). As for the
outer rami, the last article of the left foot should be examined
first. It sometimes has the form of a kind of forceps and
sometimes terminates in a sort of cushion bearing two short
obtuse spines, which perhaps represent the branches of the

*Translated from the Latin diagnosis of de Guerne ami Richard's "Revision des
Calanides <1 I'.uu Douce. ' pp. 9 and Id.

■jsixty-tivenow. many having been added since the publication of the '-Revision."

North American Species of Diaptomus. 107

forceps. All the transitions between these two forms may be
found in a series of species. Certain articles of the right
ramus may also bear divers characteristic appendages.
Finally, the terminal claw and the lateral spine of the last
article often present by their form and their position enough
peculiarities to greatly facilitate the determination.

" The right antenna of the male also furnishes some good
characters, among which figure in the first rank the append-
ages of the antepenultimate article, much varied as to form
and size (I>. bacillifer, wierzejskii, coeruleus).

" Generally speaking, the fifth pair of feet of the females
furnish the most important specific characters, although they
do not have the same technical value as in the male. At the
same time various peculiarities drawn from the conformation
of the last cephalothoracic and of the first abdominal seg-
ments and from the length of the antennae, aid greatly in the
determination."

.KEY TO THE NORTH AMERICAN SPECIES OP DiaptomUS, BASED ON
THE CHARACTERISTICS OF THE MALE.

1 (15). Antepenultimate article of right antenna without

hook-like process at tip.

2 (3). Antepenultimate article of right antenna with narrow

hyaline lamina. Second basal segment of right fifth
foot armed at the inner margin with two hook-like proc-
esses, and on the anterior surface at the apical
margin, with a hook-like process extending beyond the
middle of the first segment of the outer ramus. Inner
ramus extending barely beyond the middle of the first
segment of the outer ramus ; heavily spined at apex.
Marginal spine below the middle of the segment,
near the apical angle ; short, stout, much less than
half as long as the segment. Terminal hook very
stout, longer than preceding segment. Left leg ex-
tending about to end of first segment of outer ramus
of right leg ; second basal segment tuberculate on
inner margin. Inner ramus very long, extending about
to middle of last segment of outer ramus ; incurved,

108 Illinois State Laboratory of Natural History.

tuberculate, and armed at apex with short, blunt
spines. Last segment of outer ramus armed with a
short blunt spine and a very long spinulose one.

clavipes.

3 (2). Antepenultimate article of right antenna without

hyaline lamina.

4 (5,10). Inner ramus of right fifth foot not reaching end of

first segment of outer ramus ; sharply pointed. First
segment of outer ramus with hyaline lamina. Marginal
spine below middle of segment ; less than half as long
as segment. Terminal hook longer than the two pre-
ceding segments. Left leg extending slightly beyond
end of first segment of outer ramus of right leg ; inner
ramus reaching slightly beyond end of first segment of
outer ramus, indistinctly 2 -segmented, apex bluntly
rounded. tyrrelli.

5 (1,10). Inner ramus of right fifth foot reaching end of first

segment of outer ramus.

6 (7). Inner ramus of left fifth foot extending to base of

second segment of outer ramus, or slightly beyond.
Marginal spine below middle, near apical angle; less
than half as long as segment. Terminal hook at least
as long as the two preceding segments. Left leg reach-
ing about to middle of second segment of outer ramus of
right leg. Last segment of outer ramus armed with
forcipate structure ; inner digitiform process armed
with cushion on inner margin. pallidus.

7 (6). Inner ramus of left fifth foot reaching to middle of

second segment of outer ramus.

8 (9). Marginal spine of right leg above middle of segment,

very stout, as long as or longer than segment. Term-
inal hook almost as long as the two preceding segments
and second basal segment taken together. Inner ramus
as long as first segment of outer ramus. First seg-
ment of outer ramus with broad hyaline lamina on
inner margin. Left leg not quite reaching middle of
second segment of outer ramus of right leg. birgei.

North American Species of Diaptomus. 109

9 (8). Marginal spine of right leg below middle of segment ;

slender, less than half as long as segment. Terminal
hook longer than the two preceding segments, a sharp
angle dividing it approximately into halves. Inner
ramus reaching end of first segment of outer ramus ;
apex bluntly rounded. Left leg reaching beyond middle
of last segment of outer ramus of right leg. Last seg-
ment of outer ramus ending in a forcipate structure ;
outer digitiform process stout, armed on inner margin
near tip with cushion-like hairy process. reighardi.

10 (4, 5). Inner ramus of right fifth foot reaching well

beyond end of first segment of outer ramus.

11 (12). Inner ramus of left fifth foot long, extending beyond

middle of second segment of outer ramus ; leg itself
(disregarding terminal spines) not reaching end of first
segment of outer ramus. Marginal spine of right leg
inserted below middle of segment, near apical angle ;
much less than half as long as segment. Terminal
hook shorter than the preceding segment. piscine?.

12 (11). Inner ramus of left fifth foot short, not extending

beyond middle of second segment of outer ramus.

13 (14). Inner ramus of left fifth foot not reaching to middle of

second segment of outer ramus ; leg itself reaching end
of second segment of outer ramus of right leg. Mar-
ginal spine below middle of segment near apical angle ;
almost as long as segment. Terminal hook longer
than the preceding segment. Inner ramus of right
foot extending beyond end of first segment of outer
ramus. oregonensis.

14 (13). Inner ramus of left fifth foot reaching middle of sec-

ond segment of outer ramus ; leg itself reaching about
to middle of second segment of outer ramus of right leg.
Marginal spine below middle of segment, about half as
long as segment. Terminal hook longer than the two
preceding segments. Inner ramus of right foot ex-
tending to middle of second segment of outer ramus.

mississippiensi8.

110 Illinois State Laboratory of Natural History.

15 (1). Antepenultimate article of right antenna with hook-

like process at tip.

16 (27). Process on antepenultimate article as long as or

longer than penultimate article.

17 (20). Process curved.

18 (19). Inner ramus of right leg alone 2-segmented, extend-

ing almost to middle of second segment of outer ramus.
Marginal spine below middle, near distal angle,
smooth, about half as long as segment. Terminal hook
fully as long as the two preceding segments and the
second basal segment taken together. Second basal
segment not dilated. Left leg reaching about to middle
of first segment of outer ramus of right leg; inner
ramus barely reaching middle of last segment of outer
ramus. franciscanus.

19 (18). Inner ramus of both legs 2-segmented. Marginal

spine below middle, near apical angle ; hairy, almost as
long as segment. Terminal hook longer than the two
preceding segments, but not as long as those and the
second basal segment taken together. Second basal
segment dilated into rugose lamella. Inner ramus of
right leg extending about to middle of second segment
of outer ramus. Left leg extending about to middle of
second segment of outer ramus of right leg ; inner
ramus extending beyond middle of last segment of
outer ramus. eiseni.

20 (17). Process straight.

21 (22). Process sharply pointed. Marginal spine below mid-

dle, about half as long as segment. Terminal hook
longer than the two preceding segments. Inner ramus
of right leg extending a little beyond end of first seg-
ment of outer ramus. Left leg reaching slightly beyond
end of first segment of outer ramus of right leg ; last
segment of outer ramus with hairy cushion on inner
margin ; inner ramus extending almost to middle of
last segment of outer ramus. shoshone.

22 (21). Process blunl or swollen at tip.

North American Species of Diaptomus. Ill

23 (24). Inner ramus of right leg rudimentary, barely sur-

passing end of segment from which it arises. Mar-
ginal spine about at middle of segment, very small.
Terminal hook shorter than the very long preceding
segment. Left leg extending slightly beyond end of
first segment of outer ramus of right leg ; inner ramus
very narrow, extending about to middle of second seg-
ment of outer ramus. minutus.

24 (23). Inner ramus of right leg not rudimentary, longer

than first segment of outer ramus.

25 (26). Marginal spine well above middle of segment, about

half as long as segment. Terminal hook longer than the
two preceding segments. Inner ramus of right leg very
narrow. Left leg reaching slightly beyond end of first
segment of outer ramus of right leg ; inner ramus extend-
ing to middle of last segment of outer ramus, ashlandi.

26 (25). Marginal spine below middle of segment, less than

half as long as segment. Terminal hook very slender,
longer than the two preceding segments. First seg-
ment of outer ramus with hyaline lamina at inner distal
angle. Left leg extending about to middle of second
segment of outer ramus of right leg ; inner ramus ex-
tending barely to middle of second segment of outer
ramus. sicilis.

27 (16). Process shorter than penultimate article.

28 (33). Process the continuation of a hyaline lamina.

29 (30). Process extending at least to middle of penultimate

article. Hyaline lamina extending but little more than
the distal half of the segment. Marginal spine below
middle of segment ; shorter than segment. Terminal
hook longer than the two preceding segments but not
as long as those and the second basal segment together.
Inner ramus of right leg extending slightly beyond end
of first segment of outer ramus. Left leg extending
slightly beyond end of first segment of outer ramus of
right leg ; inner ramus extending about to middle of
last segment of outer ramus. novamexicanus.

112 Illinois State Laboratory of Natural History.

30 ("29). Process extending very slightly beyond end of article

of which it is a part. Hyaline lamina extending entire
length of segment.

31 (32). Inner ramus of right leg reaching well beyond mid-

dle of the very long first segment of the outer ramus.
Marginal spine below middle, near apical angle ; less
than half as long as segment. Terminal hook shorter
than the preceding segment. Left leg (excluding ter-
minal spines) reaching about to middle of first segment
of outer ramus of right leg. Last segment of outer
ramus terminated by two spines ; inner ramus reach-
ing well beyond end of first segment of outer ramus,
but not to middle of last segment. leptopus.

32 (31). Inner ramus of right leg rudimentary (the suture

being rarely visible), barely reaching the end of the
very short first segment of the outer ramus. Marginal
spine below middle of segment, less than half as long as
segment. Terminal hook stout, longer than the pre-
ceding segment. Second basal segment very broad,
armed at outer distal angle with a process about as
large as the inner "ramus." Left leg very short, barely
reaching end of second basal segment of right leg;
inner ramus very short, extending barely beyond end
of first segment of outer ramus. sanguineus.

33 (28). Process not the continuation of a hyaline lamina.

34 (41). Process straight.

35 (36). Process serrate on outer margin, extending beyond

middle of penultimate article. Inner ramus of right
leg very broad and short, extending but slightly be-
yond middle of first segment of outer ramus. Margi-
nal spine above middle of segment, less than half as
long as segment. Terminal hook longer than the very
long preceding segment. Left leg very short, extend-
ing barely beyond end of first segment of outer ramus
of right leg. First basal segment of both legs with
long slender spine on posterior surface. trybomi.

36 (35). Process not serrate.

North American Species of Diaptomus. 113

37 (38). Inner ramus of right leg rudimentary, extending but

slightly beyond the end of the segment to which it is
attached. Marginal spine below middle of segment,
slender, fully half as long as the very long segment.
Terminal hook shorter than the preceding segment.
Left leg (disregarding terminal spines) not reaching end
of first segment of outer ramus of right leg. Last seg-
ment with two spines : one long, slender, outcurved ; the
other short, stout. Inner ramus extending almost to
end of last segment of outer ramus. lintoni.

38 (37). Inner ramus of right leg not rudimentary, extend-

ing to middle of first segment of outer ramus or beyond.

39 (40), Inner ramus of right leg extending about to middle

of first segment of outer ramus. Marginal spine below
middle, about half as long as segment. Terminal
hook longer than the preceding segment. Second basal
segmen^ with hyaline lamina on inner margin. Left
leg (disregarding terminal spines) reaching about to
middle of first segment of outer ramus of right leg ;
inner ramus reaching end of first segment of outer
ramus, corrugate on inner margin. stagnalis.

40 (39). Inner ramus of right leg extending beyond the end of

the very short first segment of outer ramus. Marginal
spine below middle of segment, stout, longer than
segment. Terminal hook very long, stout, longer than
remainder of leg. Left leg extending beyond end
of first segment of outer ramus of right leg ; second
segment with ciliate lamina on inner margin ; inner
ramus reaching end of first segment of outer ramus.

albuquerquensis.

41 (34). Process curved.

42 (43). Process small, not reaching middle of penultimate

article. Marginal spine below middle ; rather stout,
less than a third the length of segment, Terminal hook
noticeably longer than the two preceding segments.
First segment of outer ramus with hyaline lamina on
inner margin, the inner apical angle of which is not

114 Illinois State Laboratory of Natural History.

produced. Inner ramus of right leg not reaching end
of first segment of outer ramus ; apex bluntly rounded.
Left leg reaching about to end of first segment of outer
ramus of right leg ; inner ramus reaching middle of last
segment of outer ramus, margins sinuously curved.

siciloides.
43 (42). Process stout, reaching to middle of penultimate
article or beyond. Marginal spine below middle of seg-
ment, less than half as long as segment. Terminal hook
not much if any longer than the two preceding seg-
ments. First segment of outer ramus with hyaline
lamina on inner margin, which is much produced at
the outer apical angle. Inner ramus of right leg conical,
not reaching end of first segment of outer ramus. Left
leg reaching to tip of first segment of outer ramus of
right leg. Inner ramus extending beyond middle of
last segment of outer ramus ; margins parallel ; armed
on outer margin near base with small hemispherical
process. signicauda.

KEY TO THE NORTH AMERICAN SPECIES OF DiaptomilS, BASED ON
THE CHARACTERISTICS OF THE FEMALE.

1 (18). Inner ramus of fifth pair of legs noticeably shorter

than first segment of outer ramus.

2 (10). Outer ramus distinctly or indistinctly 3-segmentrd.

3 (4,7). Inner ramus distinctly 2-segmented, the first seg-

ment very short and subquadrate ; barely reaching end
of first segment of outer ramus ; armed with two straight
hairy spines, almost as long as the ramus. Second
segment of outer ramus with small spine near base of
third segment ; spinose on both margins. Third seg-
ment armed with two stout spines, the inner hairy,
about twice as long as the outer, which is about as
long as the spine on the preceding segment. Last
thoracic segment strongly produced. First abdominal
segment longer than remainder of abdomen, greatly
dilated, armed on each side with large spine ; second
segment shorter than third. Furcal rami about as

North American Species of Diaptomus. 115

long as wide, hairy within. Antenna? extending barely
to base of abdomen. stagnalis.

4 (3,7). Inner ramus indistinctly 2-segmented.

5 (6). Terminal spines of inner ramus about half as long as

ramus. Second segment of outer ramus armed with a
single spine. Two spines on the third segment ; suture
between this and preceding segment indistinct. Inner
ramus extending beyond middle of first segment of
outer ramus ; armed at apex with two long spines.
Third segment of outer ramus armed with two very
large stout spines, the inner hairy, less than twice as
long as the outer. First abdominal segment longer
than remainder of abdomen ; armed anteriorly with
large lateral process. Antennae reaching process on
first abdominal segment. eiseni.

6 (5). Terminal spines of inner ramus not nearly half as long

as ramus. Second segment of outer ramus with a spine.
Inner ramus extending slightly beyond middle of first
segment of outer ramus. Third segment of outer
ramus hairy and about twice as long as the inner, which
is smooth. First abdominal segment longer than re-
mainder of abdomen, armed laterally with strong spines.
Antennae extending beyond tips of f ureal setae.

albuquerquensis.

7 (3,4). Inner ramus 1-segmented.

8 (9). Terminal spines of inner ramus smooth, more than

half as long as ramus, which is rounded at apex and
hairy. Second segment of outer ramus straight, as
long as or longer than preceding segment ; armed at
base of third segment with short spine, shorter than
either of the two on third segment. Inner spine of
third segment hairy, about twice as long as the outer,
which is smooth. Both spines considerably longer
than the segment itself. Last thoracic segment armed
on each side w T jth two small spines. First abdominal
segment shorter than remainder of abdomen, dilated,
armed with large spines ; second segment very short.

116 Illinois State Laboratory of Natu/ral History.

Third segment and furca] rami about equal. Antennae
reaching base of abdomen. shoshone.

9 (8). Terminal spines of inner ramus smooth, not nearly

half as long as ramus, which is hairy at apex and on
inner margin. Second segment of outer ramus curved,
barely as long as preceding segment; armed at base
of third segment with an inconspicuous spine. Third
segment armed with two short spines but slightly longer
than the segment. Last thoracic segment armed with
small spines. First abdominal segment with a sharp
spine ; longer than remainder of abdomen. Antenna?
reaching furcal rami. novamexicanus.

10 (2). Outer ramus 2-segmented.

11 (12). Inner ramus almost rudimentary, not nearly reach-

ing the middle of first segment of outer ramus. Second
segment of outer ramus considerably shorter than first ;
third segment represented by two spines, the inner
about twice as long as the outer. Last thoracic seg-
ment armed on each side with small spine. First
abdominal segment as long as remainder of abdomen ;
second segment very short ; third, longer than furcal
rami. Antennae reaching slightly beyond furca.

minutus.

12 (11). Inner ramus not rudimentary, reaching beyond the

middle of first segment of outer ramus.

13 (14). Second segment of outer ramus armed with a short

spine ; denticulate within and without. Third segment
represented by two subequal spines. Inner ramus not
nearly reaching end of first segment of outer ramus ;
hairy on inner margin ; terminal spines fully half as
long as segment. First abdominal segment dilated,
about equal in length to remainder of abdomen ; sec-
ond segment and furcal rami each longer than third
segment. piscina.

14 (IB). Second segment of outer ramus not armed with a

spine.

North American Species of Diaptomus. 117

14 (15). Inner ramus armed with very short subequal spines

and hairy at apex. Second segment of outer ramus
curved, denticulate on inner margin ; third segment
represented by two spines, the inner the longer and
about half as long as the second segment. Last tho-
racic segment produced, armed with two large spines on
each side ; penultimate thoracic segment produced into
dorsal hump. First abdominal segment as long as
remainder of abdomen, armed with large spine on
each side ; second segment shorter than the third,
which is about equal to the furcal rami. Antennae
extending about to base of abdomen. sanguineus.

15 (11). Inner ramus armed with long conspicuous spines.

16 (17). Second segment of outer ramus straight, about as

long as the first, armed with a spine at base of third
segment. Inner spine of third segment slightly the
longer. Inner ramus hairy at apex ; terminal spines
straight, hairy, about a third as long as the ramus.
Last thoracic segment armed on each side with a spine.
First abdominal segment short, unarmed. Antennas
extending to end of thorax. leptopus.

17 (16). Second segment of outer ramus straight, slightly

shorter than first ; third segment represented by two
subequal spines. Inner ramus barely as long as first
segment of outer ramus, hairy at apex, armed with
two rather long spines. Antennae extending to end of
furca. birgei.

18 (1). Inner ramus clearly reaching end of first segment

of outer ramus or beyond.

19 (22). Outer ramus 3 -segmented.

20 (21). Third segment of outer ramus small but distinct ; in-

ner of the two spines slightly the longer. Second seg-
ment curved, shorter than first ; denticulate on inner
margin ; armed with small spine at base of third seg-
ment. Terminal spines of inner ramus very long,
almost as long as the ramus. Last thoracic segment
armed with two minute spines. First abdominal

118 Illinois State Laboratory of Natural History.

segment as long as remainder of abdomen, dilated,
armed with small spines ; second segment very short ;
third segment longer than f ureal rami. Antennae
extending to furca. franciscanus.

21 (20). Third segment of outer ramus very indistinct or

aborted ; armed with two short subequal spines. Second
segment of outer ramus about as long as the first, hairy
within and without. Inner ramus reaching about to
end of first segment of outer ramus, hairy, armed with
two long hairy subequal spines. First abdominal seg-
ment shorter than remainder of abdomen, dilated but
unarmed; second segment shorter than the third,
which is longer than the furca. Antennae not reaching
end of furca. piscinae,

22 (19). Outer ramus 2-segmented.

23 (26). Second segment of outer ramus armed with a spine

in addition to the two spines representing the third
segment.

24 (25). Terminal spines of inner ramus hairy, nearly half as

long as ramus, which reaches to the end of the first
segment of the outer ramus. Second segment of outer
ramus shorter than the first, slightly curved, denticulate
within ; third segment represented by two spines, the
inner hairy, about half as long as the outer, which is
smooth. First abdominal segment longer than re-
mainder of abdomen ; second segment shorter than
third; the third longer than furca. Antennas reaching
tip of furcal rami. lintoni.

25 (24). Terminal spines of inner ramus hairy, not nearly

half as long as ramus, which is hairy at the apex. Third
segment of outer ramus represented by two spines, the
inner about twice as long as the outer. Second seg-
ment armed with a small spine. Last thoracic seg-
ment greatly produced laterodorsally ; armed on each
side with two small spines. First abdominal segment
about as long as remainder of abdomen and armed
with two large spinose processes ; second segment

North American Sjiecies of Diaptomus. 119

shorter than third and about equal to f ureal rami.
Antennae extending beyond base of furca but not be-
yond the tip. tyrrelli.

26 (23). Second segment of outer ramus not armed with

an additional spine.

27 (32). Second segment of outer ramus longer than preced-

ing segment.

28 (29). Outer of the two spines representing the third seg-

ment of outer ramus very small and inconspicuous ;
second segment shorter than the first, denticulate.
Inner ramus reaching slightly beyond end of first seg-
ment of outer ramus ; hairy on outer margin and at
apex ; armed with two rather long subequal spines.
Last thoracic segment produced laterodorsally, armed
with two spines on each side. First abdominal seg-
ment slightly shorter than remainder of abdomen,
dilated, armed on each side with a large spine ; second
segment shorter than third ; third segment and furca
about equal. Antennae reaching beyond tip of furca.

clavipes.

29 (28). Outer spine rather conspicuous.

30 (31). Terminal spines of inner ramus smooth. Inner

ramus reaching end of first segment of outer ramus ;
apex hairy ; spines small. Second segment of outer
ramus about as long as the first, denticulate, point
acute ; third segment represented by two spines. First
abdominal segment as long as remainder of abdomen,
dilated, armed with small spines ; second segment
shorter than third ; third about equal to the furca.
Antennae extending to tips of furcal setae.

oregonensis.

31 (30). Terminal spines of inner ramus hairy, subequal.

Second segment of outer ramus about equal to the
first; third segment represented by two subequal
spines. Last thoracic segment armed on each side with
two small spines ; the penultimate thoracic segment
with a small hump. First abdominal segment slightly

120 Illinois State Laboratory of Natwral History.

shorter than remainder of abdomen ; second segment
shorter than third ; third segment and furca about
equal. Antennas extending beyond end of furca but
not to tips of fureal setae. signicauda.

32 (27). Second segment of outer ramus shorter than preced-

ing segment.

33 (34). Last thoracic segment with a large dorsal process,

armed with two spines, one minute. First abdominal
segment longer than remainder of abdomen, with short
mucronate process anteriorly, and posteriorly with
large triangular process. Second segment of outer
ramus straight, hairy ; third segment represented by
two spines, the inner about twice as long as the outer.
Inner ramus noticeably shorter than first segment of
outer ramus, with two long subequal spines at the
apex. Antennae barely reaching furca. trybomi.

34 (33). Last thoracic segment without dorsal process.

35 (36). First abdominal segment longer than remainder of

abdomen, dilated, armed with small spine on each side ;
second segment very short; third segment shorter
than fureal rami. Second segment of outer ramus
shorter than the first ; third segment represented by
two spines of which the inner is the longer. Inner ramus
extending beyond end of first segment of outer ramus,
hairy, armed with two smooth subequal spines. An-
tennae extending just beyond furca. ashlandi.

36 (35). First abdominal segment about equal to remainder

of abdomen.

37 (38). Second abdominal segment very much shorter than

the third. Last two thoracic segments confluent ; the
last one armed on each side with two small spines.
First abdominal segment with large spine on each side ;
third segment longer than the second or the furca.
Second segment of outer ramus shorter than the first ;
third segment represented by two small spines, the
inner about twice as long as the outer. Inner ramus

North American Species of Diaptomus. 121

hairy, armed with two small spines. Antennae reach-
ing slightly beyond end of furcal rami. siciloides.

38 (37). Second abdominal segment slightly shorter or at

least not longer than the third.

39 (42). Furca longer than third abdominal segment.

40 (41). First abdominal segment nearly as long as remain-

der of abdomen ; dilated laterally, armed with one
small spine on each side. Second segment of outer
ramus shorter than the first ; third segment represented
by two spines, the inner the longer and pointed
obliquely outward. Inner ramus reaching end of first
segment of outer ramus ; apex hairy and armed with
two spines. Antennae reaching end of furcal setae.

reighardi.

41 (40). First abdominal segment as long as remainder of

abdomen ; dilated laterally but unarmed. Last tho-
racic segment produced, armed with one small spine on
each side. Head partially divided by a suture. Third
segment of outer ramus represented by two spines, the
inner smooth, about twice as long as the outer, which
is delicately hairy. Inner ramus hairy, armed with
two long subequal spines. Antennae reaching beyond
end of furca. pallidus.

42 (39). Furca about equal to third abdominal segment.

43 (44). First abdominal segment about as long as remainder

of abdomen and armed with small spines, equal on the
two sides. First thoracic segment armed with small
spine on each side. Second segment of outer ramus
shorter than the first ; third segment represented by
two spines, the inner about twice as long as the outer.
Inner ramus longer than first segment of outer ramus ;
hairy, armed with two spines, the inner twice as long
as the outer; margins sinuously curved. Antennae
reaching beyond tip of furca. sicilis.

44 (43). First segment of abdomen as long as remainder of

abdomen; armed with two large lateral spines, the

122 Illinois State Laboratory of Natural History.

right somewhat the longer. First two thoracic seg-
ments equal, together about half as long as entire
thorax ; last segment armed with two small spines.
Second segment of outer ramus very broad, especially
at the base. Inner ramus hairy on outer margin and
at tip, which is armed with two rather long slender
spines. Antennae reaching beyond furca.

iiiississippiensis.

Diaptomus sicilis Forbes. (PI. XXI., Fig. 1-3.)

Diaptomus sicilis, Forbes, 'S2a, p. 645, PI. VIII., Fig. 9, 20.
Diaptomus pallidus var. sicilis, Herrick, '84, p. 142, PI. Q, Fig. 18.
Diaptomus sicilis, tie Guerne et Kichard, '89b, p. 23, Fig. 13, 14; PI.

II., Fig. 13.
Diaptomus sicilis. Forbes, '90, p. 702, PI. I.. Fig. 6.
Diaptomus sicilis, Marsh, '93, p. 197. PI. III., Fig. 8, 10.

Body slender, widest in front of the middle ; suture between
head and thorax distinct. Last two thoracic segments con-
fluent ; the last one produced laterodorsally and armed on each
side with one or two small spines ; (in the male unarmed.)
Abdomen long and narrow, especially in the male, in which
the first segment is the longest and slightly the broadest. In
the female (PI. XXL, Fig. 3) this segment is fully as long as
the remainder of the abdomen, dilated, and armed on each
side with a spine ; last three segments subequal. Furcal
rami fully twice as long as broad and hairy within.

Antennae 2 5 -segmented, reaching well beyond the tips of
the furcal rami. Male geniculate antenna moderately swollen
beyond the twelfth segment ; first two segments without
special armature ; antepenultimate segment armed with nar-
row spine-like process with swollen apex, reaching to the
middle of the penultimate segment; segments 19, 20, and
21 confluent, as are also 22 and 23.

Fifth pair of legs in the male (PI. XXL, Fig. 1) rather
long and slender. First basal segment of the right foot with
a large tubercle on the posterior surface near the outer mar-
gin, bearing a minute blunt spine. Second basal segment
subquadrate, about one and a half times as long as broad.
At the beginning of the distal third of its outer margin, is a

North American Species of Diaptomus. 123

small cuticular projection bearing a delicate hair. First seg-
ment of the outer ramus subquadrate, slightly longer than
broad, the inner distal angle provided with a small semi-
elliptical hyaline lamina arising from the anterior surface of
the leg; second segment slightly arcuate, the two margins
parallel, fully twice as long as wide. Marginal spine long
and slender, slightly curved, about half as long as the seg-
ment, and inserted at the beginning of the distal third. Ter-
minal hook long, slender, and regularly curved ; very minutely
denticulate on the inner margin.

Inner ramus of the right leg either one- or two-segmented,
extending beyond the end of the first segment of the outer
ramus ; minutely hairy at the tip.

There is nothing distinctive about the basal segments of
the left leg. The first segment of the outer ramus is about
one and a half times as long as broad ; the inner distal angle
gradually rounded and minutely hairy- The second segment
is narrow, twice as long as broad ; armed at the tip with two
digitiform processes and sometimes with a much smaller
third process between the two. This segment appears very
broad and fleshy because of a cushion-like process with rugose
surface which extends beyond the inner margin of the seg-
ment for half its length. The other, upper, half is occupied
by a minutely hairy semicircular cushion.

Inner ramus of the left foot either one- or two-segmented, ex-
tending to the middle of the last segment of the outer ramus ;
hairy at the tip.

Basal segments of the fifth pair of feet in the female (PL
XXI., Fig. 2) not characteristic. The usual delicate hair is
found on the outer margin of the second basal segment.
First segment of outer ramus long and narrow, more than
twice as long as broad. Second segment almost as long as
the first, narrow, tapering to a fine point, delicately spinose
at the inner margin. Third segment wanting; represented
by two spines, both sharp and slender, the inner about twice
as long as the outer.

Inner ramus of fifth leg of female one-segmented, project-
ing slightly beyond the end of the first segment of the outer

124 Illinois State Laboratory of Natural History.

ramus, the proximal four fifths of uniform width. At the
beginning of the distal fifth of the inner margin is a rather
sharp angle, from which projects a long, slender, slightly
curved spine, about one fifth the length of the ramus.
Beyond this the ramus tapers to a blunt point, hairy at the
apex. Besides the spine already mentioned there is a smaller
one, only about half as long, having its point of insertion
very near and slightly above the first.

Length of female 1.23-1.28 mm; of male 1.00-1.18 mm.

D. sieilis closely resembles both D. ashlandi and D.
pallidus, differing from the latter, however, in the presence of
a hook on the right male antenna, and from both in the details
of structure of the fifth pair of feet of the male.

A very interesting variation was noticed in the inner rami of
the fifth pair of feet of the male. In specimens taken from
Lake Superior, at Marquette, Mich., the rami were sometimes
both one-segmented, sometimes both were two-segmented,
and at other times one ramus was two-segmented while the
other was one-segmented. Herrick (Herrick and Turner, '95)
states that all his specimens had one-segmented rami; also
that the process on the right male antenna was shorter than
described by Dr. Forbes.

Although I), sieilis is not at all uncommon, it has occurred
less frequently in the collections I have examined than have
D. siciloides Lillj., D. ashlandi Marsh, or D. oregonensis
Lillj. Marsh ('93) records D. sieilis from the Great Lakes
and from Green Lake, Wis., it being the common pelagic
species in 1890 and 1891, while in 1892 not a single specimen
was found there although the collections were made at the
same time of year. The type was described (Forbes '82a)
from Lake Michigan and had not then been found anywhere
else. In 1890 Dr. Forbes found it in Lake Michigamme, in
northern Michigan, as well as in Lake Michigan. His variety
imperfectus is D. ashlandi Marsh. In the Yellowstone Park
collections sieilis was found in considerable quantities, but
as both D. sieilis and D. ashlandi were present, it would
require a re-examination of the material to determine the
distribution of the two species in that locality.

North American Species of Diaptomus. 125

Diaptomus piscinae Forbes. (PL XXII. , Fig. 1-4.)

Diaptomus piscinas, Forbes, '93, p. 253, PI. XLL, Fig. 22.
Diaptomus piscinas, Herrick and Turner, '95, p. 74, PI. V., Fig. 13.

"A species of medium size and symmetrical proportions,
antennae reaching to the tip of the abdomen, cephalothorax
broadest about the middle, with four distinct sutures, the
posterior lateral angles not produced but armed with two
distal spines.

"The right antenna of the male is without appendage to
the antepenultimate joint, and the fifth pair of legs in the
same sex has the inner ramus well developed on both the
right and left sides. The usual length is 1.75 millimeters,
the transverse diameter 0.45 millimeters ; the abdomen with
furca is a little more than one third the length of the cephalo-
thorax.

" The fifth pair of legs of the female [PI. XXII., Fig. 2, 4] is
without especially marked characters, except that the inner
ramus, which reaches to the tip of the principal segment of
the outer, is provided with two long, stout, equal seta? more
than half as long as the ramus itself. The third joint of the
outer ramus is aborted and bears two short, stout spines,
and the joint preceding bears a slender spine outside the
base of the last. The terminal claw of this joint is simple
and nearly straight, viewed in the usual position.

"In the male the fifth pair of legs [PI. XXII., Fig. 1] has
a considerable resemblance to the corresponding append-
ages of D. leptopus, from which, however, this species differs
by its more slender form and by the absence of the antennal
hook. The peduncle of the left leg is quadrate and equal in
length to the basal segment of the outer ramus, but is nearly
twice as wide. The sides of this latter segment are parallel,
the inner terminal angle is broadly rounded and minutely
ciliate, and to the outer terminal angle is attached the second
segment of the ramus. This segment is a trifle shorter than
the preceding and less than half as wide, and bears at its tip
a stout, blunt, conical spine, whose length is equal to that of
the diameter of the ramus, and within this a long flexible

126 Illinois State Laboratory of Natwal History.

hair as long as the ramus itself. The inner ramus of this
leg is very long, reaching beyond the middle of the terminal
joint of the outer ramus. It is slightly concave towards this
ramus and terminates with a broadly rounded or subtruncate,
thickly ciliate end, forming an acute outer angle and an
obtuse inner one. Seen at right angles to this view, the tip
is simply obtusely pointed.

" The right leg of the male is without remarkable distin-
guishing characters. Basal joint of the outer ramus about
two thirds as long as the peduncle and nearly as wide; sec-
ond joint slightly longer than the peduncle, equal to the first in
width ; and the terminal claw sinuate or irregularly curved.
The stout seta on the outer margin of the second segment of
this ramus is borne at about a quarter the length of the seg-
ment from the distal end, and is approximately half as long
as the segment to which it is attached. The inner ramus is
a little longer than the basal joint of the outer. It is not
dilated or otherwise modified, but terminates bluntly, bearing
at the tip a covering of long cilia,

"The right antenna of the male is without notable dis-
tinctive characters. The antepenultimate segment is as long
as the two following taken together ; the fourth from the tip
bears two long sword-like spines at its margin, both attached
to its basal fourth ; the expanded segments are well armed
with conical spines, straight and curved, but without hooks.

" Small lakelet near Gardiner, Montana."*

This is the only one of the four species described by Dr.
Forbes ('93) which I have found in any other collections than
the original ones. In collections loaned me by Prof. L. S.
Eoss, of Drake University, Iowa, made by him at Portage
Slough, Manitoba, Canada, in June, 1895, I found quite a
number of specimens of this species, which, however, exhibit
a number of peculiarities. The fifth pair of legs in the
female are stouter and the inner ramus is relatively shorter
than in the Montana specimens, the latter not reaching to
the end of the first segment of the outer ramus as it does in the
type. The spines on the inner ramus also have a more

♦Description quoted from Forbes, '93

North American Species of Diaptomus. 127

'distinct and broader basal portion than the individuals from
Yellowstone Park. Both the inner and outer margins of the
second segment of the outer ramus are hairy in Dr. Forbes's
specimens, but much more pronouncedly so in the specimens
from Portage Slough.

The fifth pair of feet of the male are very similar to the
corresponding appendages of I), clavipes sp. nov. and D.
leptopus Forbes. Dr. Forbes notes the differences between his
species (piscina and leptopus), and from clavipes both may be
distinguished at a glance by the inner rami and the other
peculiarities mentioned in the description of that species. A
characteristic of D. piscina, and one which was neither figured
nor described, is a fin-shaped process on the middle of the
anterior surface of the second basal segment of the right fifth
foot of the male. This is armed on the inner margin with a
row of bead-like tubercles and is more distinct in the Portage
Slough specimens. This process corresponds to a similar
one in D. clavipes. The lower two thirds of the inner margin
of this segment are hairy, and at the end of the proximal
third is a small triangular projection.

The terminal hook and the marginal spine of the outer ramus
of the right male foot are both denticulate on the lower half of
the inner margin.

In the "Preliminary Pieport on the Aquatic Invertebrate
Fauna of the Yellowstone National Park, Wyoming, and of,
the Flathead Region of Montana" the inner ramus of the right
fifth leg of the male (Fig. 22) by mistake was not figured.
The description was correct but the figure did not correspond.

The first and second segments of the outer ramus of the left
fifth foot of the male are hairy on the inner margin.

The length of the Portage Slough specimens is as follows :
female, 2.11 mm; male, 2.06 mm.

Diaptomus lintoni Forbes. (PI. XXVII. , Fig. 1.)

Diaptomus lintoni, Forbes, '93, p. 252, PI. XLIL, Fig. 26-28.
Diaptomus lintoni, Herrick and Turner. *95, p. (58, PI. V., Fig. 12.

"A large red species occurring commonly with D. shoshone,
but distinguishable from it at a glance by its different shape,

128 Illinois State Laboratory of Natural History.

its longer antennas, its smaller size, and by characters derived
from the right antenna and the fifth foot of the male. The
thorax is symmetrically elliptical in shape, broadest at the
middle. The posterior angles are not produced or bifid, but
are each armed with a minute spine. The first segment of
the abdomen of the female is not especially produced, but
bears at its broadest part a minute spine on each side. The
abdomen itself is very short, its length contained about three
and one third times in that of the cephalothorax. The
antenna of the female is long and slender, 25-jointed, reach-
ing a little beyond the tip of the abdomen.

" The fifth pair of legs in this sex is similar to those of D.
shoskone, but much smaller. The inner ramus is not jointed.
It is longer than the basal joint of the outer ramus, bears
two stout plumose setae at its tip, somewhat shorter than the
ramus itself, and has likewise at its inner tip a patch of small
spines or fine hairs. The second segment of the outer ramus
with its terminal claw is two thirds as long again as the pre-
ceding segment, the breadth of the latter two thirds its length.
The third joint is indicated by a single long stout seta and
one or two smaller ones.

"In the male the geniculate antenna is relatively rather
slender, its last two joints without special appendages, its
penultimate with a slender transparent apical process, reach-
ing about to the middle of the succeeding segment, acute at
tip, but neither serrate nor emarginate. Fifth pair of
legs in the male [PL XXVII., Fig. 1] usually without inter-
nal ramus to the right leg, but this ramus sometimes repre-
sented by a small rudiment. The limb is usually slender
and its terminal claw short. The basal segment of the outer
ramus is nearly as long as the adjacent segment of the
pedicel, and the slender second segment of this ramus is
fully as long. Long lateral spine borne near the tip of this
segment. The terminal claw is about two thirds as long as
the segment, is somewhat abruptly angulated near its base
and slightly recurved at the tip. The inner ramus of the left
leg is very stout and long, reaching almost to the tip of the
outer ramus, is slightly curved outwards and has the apex

North American Species of Diaptomus. 129

minutely hairy. The basal segment of the outer ramus is
thick, two thirds as broad as long, somewhat inflated within,
where it extends downward and beyond the articulation with
the second segment as a rounded expansion covered with ex-
tremely fine hairs. Second segment of this ramus longer
than first, but only half as wide, bearing at its tip, within, a
rather small, obliquely projecting cushion covered with cilia,
and with two stout terminal spines, one short, blunt, straight,
and smooth, the other curved and plumose, its length about
half that of the segment to which it is attached.

"The total length of this species is about 2.5 millimeters,
excluding caudal seta3 ; depth, 0.42 millimeters.

"This species is closely related to D. stagnalis, Forbes,
from which it differs conspicuously by its smaller size, more
symmetrical cephalothorax, without prominent or bifid angles,
and longer and more slender antennae, with longer and more
slender appendage to the antepenultimate segment.

"In the fifth legs of the female this species differs from
stagnalis especially with respect to the inner ramus, which is
larger and longer than in the other, lacks the characteristic
segmentation of stagnalis, and bears at its tip shorter and
broader sets. In the male the terminal claw of the outer
ramus of the right fifth leg is much more slender than in
stagnalis, and the inner ramus is much less developed. The
left leg of this pair is different in a number of details, espe-
cially in the length and strength of the inner ramus and the
length and dissimilarity of the setae at the end of the outer.

" Common in lakes and pools of Yellowstone Park."*

This species is one of the three American forms in which
the inner ramus is rudimentary or wanting, the other two
being Z). sanguineus Forbes and 1). minutus Lilljeborg. It
has not been recorded from any' localities outside of those in
which it was originally found.

* Description quoted from Forbes, '93.

130 Illinois State Laboratory of Natv/ral History.
Diaptomus leptopus Fokbes.

Cyclops lonyicornis (?), Derrick, 77, p. 238, Fig. 1.

Diaptomus kentuckyensis (?), Chambers, '81, p. 48, PI. A, Fig. 12-1S;

PI. B, Fig. 19-23.
Diaptomus leptopus, Forbes, '82a, p. G46, PI. VIII.. Fig. 17-1 U.
Diaptomus castor (?), Herrick, '82, p. 221, Pi. I., Fig. 1-7; PI. II., Fig!

12, 1G.
Diaptomus longicornis var. leptopus. Herrick. '84, p. 140.
Diaptounis leptopus. tie Guerne et Richard, '89b, p. 21, PI. II.. Fig. 19;

PL III., Fig. 9.
Diaptomus leptopus, Marsh, '93. p. 195, PI. III., Fig. 4. 5.
Diaptomus leptopus, Herrick and Turner, '95, p. 64, PI. II.; PI. IX.,

Fig. 9.

Body long and slender, widest a little before the middle.
Head rather noticeably narrower than thorax, suture between
them distinct. Fifth and sixth thoracic segments confluent,
the last produced dorsally on each side into a triangular
process with a bluntly rounded apex armed with a single blunt
spine. The last thoracic segment of the male and the first
abdominal segment of both sexes unarmed. First abdominal
segment short, a little more than half as long as the succeed-
ing segment. Furcal rami about one and a half times as
long as wide, hairy within.

Antennre 25-jointed, extending to the tip of the furcal rami.
The male prehensile antenna rather thickly swollen, the first
segment without armature, the other segments armed as fol-
lows : 2, with a short seta and a sense-club ; 3, short seta and
sense-club ; 4 and G, long spine ; 5 and 7, long seta and sense-
club ; 8, long spine and very short spine; 9, long seta, long
spine, and sense-club ; 10 and 11, process and long spine;
12, long spine, very short spine, and sense-club ; 13, process,
long spine, and sense-club; 14, long seta, long spine, and
sense-club; 15, process, short seta, long spine, and sense-
club; 16, process, long spine, long seta, and sense-club ; 17,
process and short thick spine; 18, process; 19,. 20, and 21
(completely ankylosed), a process, a long seta, and a very
short spine; 22 and 23 (completely ankylosed), a narrow
hyaline lamina produced into a hook which extends but little
beyond the end of the segment, and two long setae ; 24, two

North American Species of Diaptomus. 131

long setae; and 25, four long set 33 and a sense-hair. Some
of the setae on the last segments are sparsely hairy.

Second basal segment of the right fifth leg of the male sub-
quadrate, about twice as long as wide ; a delicate hair at the
outer margin a short distance above the distal angle. First
segment of the outer ramus somewhat narrower than the
second basal segment, about twice as long as wide; sec-
ond segment very long and narrow, about three times as
long as wide. Marginal spine slender, about one third the
length of the segment, inserted about half its length above
the outer distal angle of the segment. Terminal hook slender,
regularly curved, about as long as the preceding segment;
distal half of inner margin denticulate.

Inner ramus of right fifth foot one-segmented, reaching
almost to the end of the first segment of the outer ramus ;
apex broadly triangular and minutely hairy.

Second basal segment of the left leg of the male subquad-
rate, slightly broader than long ; provided with a delicate hair
a short distance above the outer apical angle. First segment
of the outer ramus irregular in form, about one and a half
times as long as broad, with two rounded protuberances, the
one forming the inner apical angle delicately hairy. Second
segment long and narrow, almost as long as the preceding
segment and a fourth as wide as long; delicately hairy
at the inner margin ; armed at the apex with a short, thick,
blunt digitiform process, and a long curved spine as long as
the segment itself and hairy at the inner jnargin.

Inner ramus of left fifth leg long and narrow, extending
beyond the middle of the second segment of the outer ramus ;
margins sinuous ; apex triangular, hairy.

Second basal segment of the fifth pair of feet in the female
with the usual marginal hair. First segment of the outer
ramus subquadrate, about twice as long as wide ; second seg-
ment narrow, about as long as the first, tapering to a rather
blunt point, finely dentate on the inner margin and with a
single tooth on the outer, opposite the last tooth on the inner
margin; third segment small but distinct, armed with two
short sharp spines, the inner slightly longer than the outer.

IB 2 Illinois State Laboratory of Natural History.

Just without these, on the second segment, is a third spine,
shorter than either of the other two.

Inner ramus of fifth leg of female one-segmented, extend-
ing beyond the end of the first segment of the outer ramus ;
apex hairy ; armed with two long subequal spines hairy on
both margins and about a third the length of the ramus.

Length of female 1.89 mm. ; of male 1.83 mm.

Breadth of female 0.70 mm. ; of male 0.60 mm.

The numerous published figures and descriptions of this
species have probably made it well known to all students of
North American Centropagidce. The synonymy, however, is
interesting. In the Geological and Natural History Survey
of Minnesota, Herrick ('77, p. 238) describes and figures
"A New Cyclops." It is evident at a glance that this is a
Diaptomus, but of what species cannot be determined. In
"Microscopic Entomostraca " (Herrick, '79, p. 90) he refers
to this "Cyclops" and says, "In the Eeport of the Geological
and Natural History Survey of Minnesota for 1878 it
[Diaptomus longicornis] was mentioned and a figure given,
but erroneously called Cyclops." In a "Final Eeport on the
Crustacea of Minnesota" (Herrick, '84, p. 140) he makes D.
leptopus Forbes a variety of D. longicornis Herrick, estab-
lishing a second variety, similis (Plate Q, Fig. 5-7). In his
" Synopsis of the Entomostraca of Minnesota" (Herrick and
Turner, '95) he recognizes D. leptopus Forbes as a distinct
species, making 1>. longicornis var. leptopus a synonym ;
although in this same work I>. longicornis var. similis Her-
rick is not set up as a species, neither is the name regarded
as a synonym. The figures (Herrick '84, PI. Q, Fig. 5-7) are
not well drawn, but it is not likely that this form is leptojjus.
D. similis is referred to once (Herrick and Turner '95, p. 58)
in connection with D. franc iscanus Lilljeborg. Diaptomus ken-
tuckyensis Chambers ('81) is also quite possibly D. leptopus,
although the description is very vague and the figures are
inaccurate.

North American Species of Diaptomus. 133

Diaptomus sanguineus Forbes. (Pis. XXIII., XXIV.,
and XXV.)

Diaptomus sanguineus, Forbes, '76. pp. 15, 16, 23, Fig. 24, 28-30.

Diaptomus sanguineus, Forbes, '82a, p. 647. PI. VIII., Fig. 1-7, 13.

Diaptomus armatits(?), Herrick. '82, p. 223. Fig. 1, a, b.

Diaptomus armatus^?), Herrick, '84, p. 139.

Diaptomus sanguineus, Herrick, '84, p. 138, PI. Q, Fig. 12.

Diaptomus minnetonka, Herrick, '84, p. 138, PI. Q, Fig. 8-10.

Diaptomus sanguineus, de Guerne et Richard, '89b, p. 20, Fig. 9-11 ;

PI. IV., Fig. 24.
Diaptomus sanguineus, Marsh, '93, p. 195, PI. III.. Fig. 1-3.

A rather large species, one fourth to one third as wide as
long. The cephalothorax widens gradually to the third seg-
ment (being broadest at the suture between that segment and
the fourth), then narrows less gradually to the abdomen. In
the male the thorax is less uniform in breadth than in the
female. The last cephalothoracic segment is greatly pro-
duced on each side laterodorsally and bears a large spine,
slightly swollen at the base, varying in length from that of
the segment to one fourth its length. On the same segment
and midway between the outer spine and the abdomen is
another broader and shorter spine. Both of these spines are
slightly curved. In the female (PL XXIV., Fig. 3) they are
generally quite noticeably larger than in the male. On
the first abdominal segment is still another spine, slightly
outcurved and pointing outward, about as large as the sec-
ond of the spines mentioned above. In the female the
penultimate cephalothoracic segment bears a dorsal hump at
its anterior margin (PI. XXIV., Fig. 5, 6). This is wanting
in the male. The abdomen is produced dorsally and ven-
trally at the anterior part, making it look like a keel (PI.
XXIV., Fig. 1, 2), the keel being most pronounced on the
ventral side. The egg-mass is large and elliptical, with the
major axis transverse to the body.

Antennae 25-segmented, the seventeenth or eighteenth seg-
ment reaching about to the base of the abdomen. The right
male antenna is thickly swollen beyond the geniculate joint.
The last two segments have no special armature, but the
antepenultimate one (PI. XXIII., Fig. 6-8) is armed at the

134 Illinois State Laboratory of Natural History.

inner distal angle with a short thick recurved hook with
smooth edges, extending hut little heyond the joint. This is
merely the continuation of the hyaline lamina at the side of
the segment.

Second basal segment of the right fifth leg of the male
(PI. XXIII., Fig. 1-5), seen from behind, irregularly trape-
zoidal in form, very broad distally, and about twice as long
as its narrowest part is wide. On the outer distal angle of
this segment is another projection, equal to or greater in
length than the inner ramus. This also shows great varia-
tion, and is either rounded or acute or even acuminate at
the apex. First and second segments of outer ramus sub-
quadrate, the second about as wide as the first and about two
and a half times as long. About a third the length of the
second segment from its base is a considerable contraction,
the width here being about half the width of the broadest part.
Slightly below the middle, on the outer margin, is a spine,
minutely serrate at the inner edge. This is generally long
and straight, about half the length of the segment, but varies,
and is sometimes shorter, thicker, curved, and less than one
third the length of the segment (PL XXIV., Fig. 4 ; PI. XXY.,
Fig. 3-5). Terminal hook rather long and slender, slightly
and sometimes sinuously curved, about one and a fourth
times the length of the preceding segment. The inner margin
is serrate, beginning about the middle of the hook and con-
tinuing to the tip.

Inner ramus of the right fifth foot wanting, a peculiarity
rarely found among the American species of Diaptomus, but
approached most closely by I), lintoni Forbes and D. minutus
Lilljeborg, in which the ramus is very small, almost rudi-
mentary. The ramus is represented by an immovable spine,
minutely spinose at the tip. This is greatly diverse in shape
and sometimes gives indications of a joint (PI. XXIII., Fig.
2), as if a case of ankylosis.

Left fifth foot of the male biramose; second basal segment
quadrate, with a short thick spine just above the outer distal
angle. Second segment of outer ramus irregularly subquad-
rate, about two thirds as wide as long, provided at the inner

North American Species of Diaptomus. 135

margin with a cushion-like protuberance densely covered with
minute hairs. This segment is produced into two spines,
forming a forcipate structure. The inner spine is slightly
shorter than the main part of the segment, thick, incurved,
and movable, and armed on its outer margin and on the distal
third of the inner one with minute hairs. The outer spine is
immovable, ending in a blunt point, and its curve is rather
more pronounced than that of the inner one.

Inner ramus of left fifth foot one-segmented, straight, and
armed with minute hairs at the apex. It is about three times
as long as broad and reaches beyond the middle of the second
segment of the outer ramus.

First basal segment of the fifth foot of the female (PI. XXV.,
Fig. 1,-2") subquadrate, slightly longer than broad, bearing
a short thick spine near the outer distal angle. The distal
segment is also subquadrate and bears the usual delicate hair.
Outer ramus two- jointed, the first segment oblong, about
twice as long as wide ; second segment in the form of a thick
incurved hook, with a broad, quadrate basal portion. The
hook is about three times as long as its greatest breadth, the
distal fourth of the inner edge armed with a variable number
of teeth (8-15). Third segment wanting, represented by two
spines ; the outer short, thick, about one third the length of
the segment ; the inner rather longer and more slender, sin-
uously curved, and about half as long as the second segment.

Inner ramus of fifth foot of female straight, one-segmented,
about four times as long as broad ; armed at the tip with two
smooth spines of almost equal length and but slightly curved.
The tip of the ramus is delicately hairy.

Length of female 1.4-2.12 mm; of male l.-2."mm.

Breadth of female .4-.43 mm; of male .3-.33 mm.

The synonymy of this species is almost as complicated as
that of D. leptopus. First described by Dr. Forbes (76), it
was next described under two different names (D. sanguineus
and D. minnetonka) by Herrick ('84). I am also led to
believe very strongly that Herrick's D. armatus is nothing
but a variant of D. sanguineus. The descriptions and figures
(Herrick, '82, p. 223, Fig. 1, a and b) seem to me to be

136 Illinois State Laboratory of Natural History.

without specific value. The following, taken from Herrick and
Turner '95a, p. 72, is his most complete description. "It
appears to be allied to sanguineus . The antennae are said to be
shorter than the body, the caudal stylets narrow, the right
male antenna has a hook upon its antepenultimate joint
and is strongly geniculate. But the one feature which may
determine the species is the existence of a tooth or spur near
the base of the claw of the right fifth foot of the male."

In collections from Phelps Lake, Havana, 111., made May
18, 1894, occurred a single male specimen of a variant of D.
sanguineus which might easily be described as a new species
if the spine at the base of the terminal hook were taken as
the one specific characteristic to which all others must be
subordinated. This spine is straight and minutely dentate
on both margins. In all other respects, except a slight dif-
ference in the length of the terminal hook, the specimen is
a normal D. sanguineus. The fifth pair of legs is shown in
PI. XXV., Fig. 5. The occurrence of this specimen, taken in
connection with the loose descriptions of armatus, has led me
to believe in the identity of Herrick' s species and this variant.

In regard to D. minnetonka, Marsh ('93) points out that
it is probably but a variety of D. sanguineus. In his "Synopsis
of the Entomostraca of Minnesota" Herrick says : "We are
inclined to agree with Marsh that this form is but one of the
many variations of 1>. sanguineus" ; but he nevertheless retains
minnetonka as a species name instead of making it a synonym
of sanguineus.

Diaptomus sanguineus occurs in early spring in standing
water in connection with D. stagnalis Forbes, from which it
may be distinguished at a glance by the difference in size,
D. stagnalis being about twice as large as D. sanguineus. The
latter is generally a deep red, but D. stagnalis is often blue,
with abdomen and antennas a brilliant red.

The theory of Herrick (Herrick and Turner, '95) in regard
to the transition of forms, "beginning with J >. stagnalis and
passing through several varieties to I), sanguineus later in
the season," will not hold owing to the fact that sexually
mature specimens of both species have been found in the
same pools at the same time.

North American Species of Diaptomus. 137

The collection from which the variant mentioned above
was taken, made in May, 1894, consisted almost entirely of
D. sanguineus. Collections from the same waters made in
July, 1896, did not contain a single individual of this species,
but D. siciloides Lilljeborg and D. pallidas Herrick, were
present in immense numbers.

VARIATION IN D. SANGUINEUS FORBES.

Plates XXIII. , XXIV., and XXV. were prepared before the
thesis work proper was undertaken and exhibit the results of
a study in variation. From these figures it will at once be
evident that D. sanguineus is an unusually variable species,
and without the intermediate forms the extremes might
almost be regarded as distinct. The specimens examined
were all from the collections of the Biological Station at
Havana, so that the variations are probably not so great as
they would be if widely separated localities were represented.
Especial attention was given to variations of specific char-
acters, and most particularly to the relative proportions.

The second basal segment of the right leg of the male,
which is usually very broad, in fact one of the most charac-
teristic features of the male, is shown in PL XXIII., Fig. 2, to
be sometimes of very ordinary width, the other extreme being
shown in PI. XXIV., Fig. 4. The relative position and length
of the projection on the outer distal angle of this segment
also vary a great deal, the extremes noted being shown in PI.
XXIII., Fig. 1 and 2.

The marginal spine of the outer ramus of the right fifth leg,
the position, relative length, and characters of which are of
specific value in most species, lacks such value almost entirely
in D. sanguineus. The extreme variation is shown in PI.
XXIV., Fig. 4, and PI. XXV., Fig. 3.

The inner ramus of the right fifth leg, though always very
short, varies in length from that shown in PL XXIV., Fig. 4, to
that in PL XXIII., Fig. 2, on the latter of which is also shown
a rather clearly marked suture which is usually wanting.

The variation in the size of the males is indicated by the
drawings of the fifth pair of legs. (See PL XXV., Fig. 3-5,
and PL XXIV., Fig. 4.)

138 Illinois State Laboratory of Natural History.

The antepenultimate article of the prehensile antenna (PL
XXIII., Fig. 6-8) is not so variable, but still quite a differ-
ence may be noted in the width of the hyaline plate and in
the relative lengths of the segments.

In the female the variation in size is even greater than
in the male, the fifth legs being shown in PL XXV., Fig. 1, 2.
The variation in the "hump" of the female is slight (PL
XXIV., Fig. 5, 6), as is also that of the first abdominal seg-
ment (PL XXIV., Fig. 1, 2).

While I have found no variation whatever in the color of
D. sanguineus, all of the specimens I have seen alive being a
bright uniform red, as were also those examined by Dr.
Forbes (76), and by Gissler ('81), Gissler later ('81a) found
individuals colored as follows : body and legs bluish, an-
tenna? and furca red, and abdomen yellow. Herrick says
in the description of D.minnetonka (Herrick and Turner, '95),
which is a synonym of D. sanguineus, "color dark." In the
same work, in his description of D. sanguineus, he says
"brilliantly colored." According to my observation color is
of no certain specific value in Diaptomus, but it may be that
there are definite seasonal variations — a subject which I have
not investigated.

Diaptomus stagnalis Forbes. (PL XXVIII., Fig. 2.)

Diaptomus stagnalis, Forbes, '82a, p. 646, PL VIII., Fig. 8, 10-12, 14.
Diaptomus giganteus, Herriek,'82,p. 222, PI. II., Fig. 3, 11, 15.
Diaptomus stagnalis, Herrick. "84, p. 139, PI. Q, Fig. 11, 13.
Diaptomus stagnalis, de Guerne et Richard, '89b, p. 23, PI. IV.. Fig. 14.

Head distinct from thorax; fifth and sixth thoracic seg-
ments confluent. Lateral angles of last thoracic segment
strongly produced backward, each angle bilobed, the outer
lobe about twice as large as the inner; (in the male this seg-
ment is salient.) Abdomen peculiar in that there is a sudden
narrowing at the beginning of the third segment. First
abdominal segment armed with a large spine on each side
(in the male unarmed) ; second and third segments of the
abdomen subequal, about twice as wide as long. Furcal
rami subquadnite, hairy within. Furcal seta rather short,

North American Species of Diaptomus. 139

densely plumose. There is but little difference in the length
of the abdominal segments of the male.

Antennae 25-segmented, reaching to the middle of the
abdomen. Prehensile antenna of the male (PI. XXVIII.,
Fig. 2) thickly swollen anterior to the twelfth article, with
armature as follows: segments 1 and 5, long spine and
sense-club; 2, three long spines and sense-club; 3, short
seta; 4 and 6, long spine; 7, short seta and sense-club; 8
and 12, long spine and short spine; 9, long spine, short
seta, and sense-club; 10, 11, 13, and 17, process and
long spine; 14 and 16, long spine, short seta, and sense-
club ; 15, process, two long spines, and sense-club ; 18, proc-
ess ; 19, 20, and 21 (ankylosed, with the sutures indistinctly
indicated), two processes, a stunted spine, and a long seta;
22 and 23 (ankylosed), a broad hook-like process not reach-
ing the end of the penultimate segment, and four setae; 24,
two setae; and 25, four setae, a sense-hair, and a sense-club.

Second basal segment of the right fifth foot of the male
subquadrate, about twice as long as wide ; on the posterior
surface a large smooth hyaline lamina occupying about a
third of the inner margin near the middle, and near the outer
distal angle a minute cuticular process bearing a delicate
hair. First segment of the outer ramus almost three times
as long as broad ; second segment about as long as the first
and for about the proximal third nearly as wide, but beyond
this considerably broader. Marginal spine near the outer
distal angle ; straight, very strong and thick, little less than
half as long as the segment. Terminal hook rather short
and very stout, irregularly curved, heavily and closely den-
ticulate at the distal half of the inner margin.

Inner ramus of the right fifth leg spatulate, not nearly
reaching the middle of the first segment of the outer ramus ;
apex rounded, armed with a few strong spines.

Second basal segment of the left fifth foot armed at the
outer margin, a short distance above the distal angle, with a
short, thick, pointed spine. First segment of the outer ramus
about three times as long as wide, armed at the distal third
of the inner margin with a few strong hairs. Second segment

1 40 Illinois State Laboratory of Natural History.

about half as long as the first, having on the inner margin
two cushion-like processes (the upper, smaller one hairy, and
the lower densely tuberculate), and being armed at the tip
with two processes forming a forcipate structure, the outer
broad, plowshare-shaped, the inner a long and narrow spine,
hairy within.

Inner ramus of left fifth foot one- segmented, of the same
width throughout, with a broadly rounded tip ; inner margin
rugose.

Second basal segment of the fifth foot of the female with
the usual delicate hair at the outer margin. First segment
of outer ramus short and broad. Second segment large,
about one and a half times as long as the first, armed on the
middle third of the inner margin with seven or eight very
large, strong, pointed spines, and on the outer margin and
opposite the upper spines of the inner margin with three or
four spines. Third segment distinct, armed with two spines,
the outer one short, thick, sharp, smooth, the inner one about
twice as long and armed with a few rather strong spinules.
Just without these spines, on the second segment, is a shorter,
smooth spine.

Inner ramus of the fifth foot of the female distinctly two-
segmented, the first segment subquadrate, the second as wide
as the first and nearly twice as long, and armed at the tip
with two thick heavy spines reaching to the end of the second
segment of the outer ramus. These spines are armed with
heavy spinules. Disregarding the spines, the ramus reaches
just to the end of the first segment of the outer ramus.

Length of female 4.0-4.5 mm. ; of male 3.5-4 mm.

This Diaptomus is the largest of the American species and
a very beautiful one. Dr. Forbes states in his original des-
cription ('82a) that "all were red throughout." Specimens
taken in April, 1897, from ponds south of Urbana, 111., when
they were in the height of sexual activity, were colored as
follows: thorax and anterior appendages (all but the first
pair of antenna') blue ; first pair of antenna, fifth pair of
legs (in the male), and abdomen red. In the female all the
legs were blue.

North American Species of Diaptomus. 141

The pool from which they were taken was particularly rich
in decaying vegetable material and received the drainage of a
pasture in which cattle and horses were allowed to graze.
The water literally swarmed with Volvox; and Diaptomus,
Cyclops, and insect larvae were very abundant. The food sup-
ply was practically inexhaustible and the specimens taken
were unusually large.

Diaptomus shoshone Fokbes. r (Pl. XXVI., Fig. 1-3.)

Diaptomus shoshone, Forbes, '93, p. 251, PI. XLIL, Fig. 23-25.
Diaptomus shoshone, Herriek and Turner, '95, p. 61, PI. V., Fig. 11.

"A very large and robust species. Thorax broadest in
front, across the maxilla?, tapering gradually, with little con-
vexity, to the posterior third. In the female the angle of the
last segment is bifid, both projecting points being minutely
spinose at tip. The first segment of the abdomen (PL XXVI. ,
Fig. 1) is laterally expanded, the expansion of the left side
with a minute spine at the apex, behind, that on the right
produced at the same point into a small, prominent, rounded
tubercle, 0.03 millimeter in length, about as broad as long,
making this first segment somewhat unsymmetrical. This is
not merely a modified cuticular appendage, but is penetrated
by the hypodermis. Egg-mass very large, obovate (narrowest
forward).

"Eight antenna of male robust, the last two joints without
special appendages, antepenultimate with a very long inartic-
ulate process at its outer apex, extending beyond the tip of
the penultimate and to the middle of the last segment. The
margins of this process are smooth, but it is broad and
emarginate at the tip.

" The fifth pair of legs in the male resemble the correspond-
ing appendages of Diaptomus stagnalis, but differ notably in
detail. The left ramus of the right leg is borne at the inner
terminal angle of the second joint ; is longer than the joint
following ; is armed at the apex with a few small acute spines ;
and bears upon its outer margin, near the tip, a broad fas-
cicle of delicate hairs. The basal joint of the outer ramus is
two thirds the length of the second joint of the peduncle,

142 Illinois State Laboratory of Natural History.

and without hairs or spines of any description. The second
joint of this ramus is about equal in length to the second
joint of the peduncle, and bears on its outer margin, close to
the tip, the usual stout seta, which is two thirds as long as
the joint to which it is attached. The terminal claw is not
regularly curved, but is nearly straight for the basal three
fourths. The left leg is biramose, the inner ramus straight,
slender, extending about to the middle of the second joint of
the outer, and armed at its tip. The second joint of this
ramus is as long as the first, if measured from the tip of the
apical spine. This spine, seen from behind, is stout, conical,
rather blunt, and has opposed to it within, projecting from the
inner angle of the segment, a stout, curved seta, slightly
plumose on its distal half. Between these, but more closely
applied to the outer spine, is a hemispherical cushion-like
elevation, set with small, short spinules. On the basal half
of the inner margin of this terminal segment is also a much
larger hemispherical cushion, but with longer and more slen-
der hairs, while the terminal half of the inner margin of the
segment preceding is also moderately inflated and covered
with delicate hairs.

"The antenna? of the female are 25-jointed, as usual,
and reach to the base of the abdomen. The legs of the fifth
pair (PL XXVI., Fig. 2) closely resemble those of stagnalis,
but have the terminal sette of the inner rami much less devel-
oped. This ramus is a little shorter than the basal joint of
the outer ramus, and of about half its diameter. It bears at
its tip two stout setae equaling the ramus itself in length, plu-
mose under a high power, and has, in addition, at its inner
tip and on the inner margin adjacent, a patch of delicate
hairs and spines. The second joint of the outer ramus is as
long as the first, if measured to the tip of its terminal claw!
The latter is nearly straight, very slightly recurved. This
joint bears a single spine at its outer distal angle, just within
which is the rudiment of the third segment of the ramus, which
bears two spines similar to the above, the inner of which is the
longer, the outer itself being longer than the adjacent spine
of the second joint. Adults of both sexes are blood-red
throughout except the egg-sac of the female, which is purple.

North American Species of Diaptomus. 143

"Dimensions of female: Length to. tip of caudal setae,
3.1 millimeters; abdomen, with setae, 1.16 millimeters, with-
out, 0.67 millimeters; thorax, 1.95 millimeters in length;
depth, 0.725 millimeter; width, 1 millimeter.

" Male averaging scarcely smaller, but somewhat differ-
ently proportioned: Thorax, 1.85 millimeters in length;
depth, 0.58 millimeter; width, 0.08 [1.08]* millimeter;
abdomen, without setae, 0.745 millimeter; with setae, 1.35
millimeters in length.

"Especially abundant in Shoshone Lake, but occurring in
other lakes and even in pools of some size in Yellowstone
Park."t

The drawings here given are in some cases the same as
those in the original description with unimportant correc-
tions or additions, but two new figures (PI. XXVI. , Fig. 1,
3) have been added. I have not found this species in any
collections except those from Yellowstone Park and the Flat-
head region, in which it is rather abundant.

A few points may be added to the original description. In
the female the first basal segment of the fifth pair of legs
bears a short sharp spine on the outer margin a short dis-
tance above the distal angle. Both spines of the rudiment-
ary third segment of the outer ramus are distinctly spinose
on the inner margin. The first abdominal segment is almost
as long as the remainder of the abdomen ; the second segment
very short, about half as long as the succeeding segment or
the furca. Furcal rami about one and a half times as long
as wide and hairy within. My observations differ from those
of Prof. Forbes in that, as a rule, the abdomen of the female
is not asymmetrical, the first segment bearing on each side a
small tubercle armed with a minute spine. In the male the
first abdominal segment is very slightly dilated laterally but
unarmed, and about half as long as any one of the five suc-
ceeding segments, which differ very little in length. The
furcal rami are fully twice as long as wide and hairy within.

*The 0.08 in the original description is probably a typographical error, since the
sperinflns measured by myself were about 1.08 millimeters in length.

tDescription quoted from Forbes, '93.

144 Illinois State Laboratory of Natural History.
Diaptomus pallidus Herrick. (PL XXVII., Fig. 3.)

Diaptomus pallidus, Herrick, *79, p. 91, PI. II.
Diaptomus pallidus, Herrick, '83a, p. 3S3, PL VII., Fig. 1-6.
Diaptomus pallidus, Herrick, '84, p. 142, PI. Q, Fig. 17.
Diaptomus pallidus, de Guerne et Richard, '89b, p. 62, Fig. 34.
Diaptomus pallidus, Marsh, '93, p. 196, PI. III., Fig. 6, 7, 9.
Diaptomus pallidus. Herrick and Turner, '95, p. 73, PI. IV, Fig. 1-6;
PI. V., Fig. 10; PL XIII., Fig. 17.

Of medium size, slender; cephalothorax widest near the
middle ; bead partially divided by a suture ; suture between
bead and thorax distinct. Fifth and sixth thoracic segments
confluent ; last thoracic segment produced laterodorsally,
bearing a small spine on each side. First abdominal seg-
ment unarmed but dilated laterally (not dilated in the male),
about as long as the remainder of the abdomen ; second
segment the shortest. Furcal rami hairy within.

Antennae 25-segmented, reaching about to the tips of the
furca or slightly beyond. Male prehensile antenna moder-
ately swollen ; no special armature on the last three seg-
ments ; segments 19 and 20 ankylosed, armed with a process
and a long seta; 21, 22, and 23 ankylosed, armed with two
long setae; 24, with two long setae; and 25 with four long
setae and a sense-club. Some of the antenna! setae are
very minutely and sparsely hairy.

First basal segment of right fifth foot of male (PI. XXVII.,
Fig. 3) with large tubercle bearing a small spine on the pos-
terior aspect ; second basal segment as usual, about equal in
length to the first. First segment of the outer ramus sub-
quadrate, about as long as wide ; second segment about as
wide as the preceding and about one and a half times as
long, bearing on the inner margin, at the end of the proxi-
mal third, a small sharp-pointed cuticular projection. The
outer margin of this segment is almost straight to the begin-
ning of the distal third, where a sharp angle is made from
which springs the marginal spine. This spine is sharp,
slender, slightly curved, a little more than one third the
length of the segment. Terminal hook slender, about^ one
and a half times as long as the second segment ; not regularly

North American Species of Diaptomus. 145

curved, but with a sharp angle at the beginning of the distal
third ; minutely denticulate within.

Inner ramus of right fifth foot one-segmented, slender,
narrowing gradually from base to tip, extending but slightly
beyond the proximal third of the second segment of the outer
ramus; hairy at the apex and very delicately denticulate on
the outer margin.

Basal segments of left fifth foot subquadrate, the second
slightly longer than the first and both slightly longer than
broad; second segment delicately tuberculate dli the inner
margin. First segment of outer ramus about half as wide
and three fourths as long as the basal segment. Second seg-
ment about as long as the first, and very similar to the cor-
responding segment of D. sicilis Forbes, from which it differs,
however, in its armature. This consists of a movable claw,
blunt or slightly thickened at the tip, forming a forcipate
structure with an inner cushion-like process. The claw
usually lies close against this and is difficult to make out.
It is hairy on both margins.

Inner ramus of the left fifth foot one-segmented, hairy at
the apex and delicately denticulate on the outer margin,
extending to the end of the first segment of the outer ramus
or slightly beyond it.

Second basal segment of the fifth foot of the female with
the usual hair at the outer distal angle. First segment of the
outer ramus subquadrate, about twice as long as broad.
Second segment about as long as the first, tapering to a blunt
point ; inner margin denticulate. Third segment wanting,
represented by two spines, the inner about twice as long as
the outer and smooth, while the outer is delicately hairy.

Inner ramus of fifth foot of female one-segmented, reach-
ing the end of the first segment of the outer ramus ; hairy at
the apex and within, and armed at the tip with two long sub-
equal delicately hairy spines.

I have found specimens from the Illinois Eiver at Havana
with the inner ramus of the right fifth foot reaching barely
beyond the end of the first segment of the outer ramus. The
first basal segment of the left foot of the male is provided with

146 Illinois State Laboratory of Natural History.

a hyaline lamina ending in a pointed spine-like projection;
and the second basal segment is tuberculate at the inner
margin, as is also the outer margin of its inner ramus. All
of these differences are quite constant but not of sufficient
importance to constitute even a variety.

D. pallidus was found in immense numbers in connection
with D. siciloides Lilljeborg during the entire time of my stay
at the Biological Station at Havana — that is July and part of
August, 1896. So far as I was able to ascertain, siciloides
was slightly the more abundant, but the difference was not
Very evident.

Herrick's original description of D. pallidus ('79) was very
indefinite, and the establishment of the species really dates
from 1893, when Marsh figured and described it in a manner
to make it recognizable by later students. De Guerne and
Eichard ('89b) place it among their "species insufficiently
described."

Diaptomus albuquerquensis Herrick. (PI. XXYIL, Fig.
2, 4.)

Diaptomus albvquerquensis, Herrick. '95, p. 45. Fig. 16-26.
Diaptomus albuqurrquensis, Herrick and Turner, "95, p. 67, PI. VI.,
Fig. 1-3; Pi. VII., Fig. 1-11.

A medium-sized species. Cephalothorax widest about the
middle. Suture between head and thorax distinct. Last
two thoracic segments, seen from above, indistinctly conflu-
ent, the last one produced laterodorsally and armed on each
side with two rather long spines ; in the male produced but
but very slightly and armed with only one spine on each side.
First abdominal segment in the female longer than the
remainder of the abdomen, dilated laterally, and armed on
each side with a single spine ; second and third segments
subequal; each shorter than the furcal rami, which are
barely twice as long as wide and hairy within. First abdomi-
nal segment in the male short, a little more than half as long
as any one of the succeeding three segments ; dilated very
slightly, and armed on each side with a spine; fifth segment
about as long as the first. Furcal rami barely twice as long
as wide and hairy within.

North American Species of Diaptomus. 147

Antennae of the female 2 5 -segmented, extending well be-
yond the tips of the furcal setae ; somewhat shorter in the
male, reaching about to the tips of the furcal setae. Eight
male antenna moderately swollen beyond the thirteenth seg-
ment. Beyond the twelfth segment the antenna is armed as
follows: 13, with large process; 14, process, short seta, and
very long seta; 15, very short stunted spine, short seta, and
long seta; 16, a short and a long seta; 17, process, short
seta, and long seta ; 18, large process ; 19 and 20 (completely
ankylosed), short stunted spine and long seta; 20, 21, and
22 (also completely ankylosed), two setae, and a hooked
process extending beyond the middle of the penultimate
article; 24, two seta?; and 25, four setae.

Left fifth leg of the male (PL XXVII. , Fig. 4) short, not
reaching to the end of the second segment of the outer ramus
of the right leg. First and second basal segments subequal,
the first armed at the middle of the outer margin with a
rather long sharp spine ; the second slightly broader than
the first, and provided a short distance above the outer distal
angle with the usual delicate hair, and at the middle of the
inner margin with a small hyaline plate. First segment of
the outer ramus about twice as long as wide ; outer margin
arcuate, inner margin convex and delicately hairy. Second
segment racket-shaped, the broad basal half being almost
circular ; hairy on the inner margin. The digitiform termi-
nal half is blunt and delicately denticulate on the margin.
From the anterior aspect projects a delicately hairy spine
about as long as the digitiform process, but more acute and
pointing inward.

Inner ramus of left fifth leg short, one-segmented, barely
reaching to the end of the first segment of the outer ramus ;
margins slightly sinuous ; apex bluntly rounded, very deli-
cately hairy, the hairs at the apical angles being somewhat
stouter and spine-like.

First basal segment of right fifth leg of male subquadrate,
slightly longer than broad ; armed at the outer distal angle
with a stout, sharp spine pointing straight outward. Second
basal segment subquadrate, about equal to the first, and

148 Illinois State Laboratory of Natural History.

armed on the outer margin, a short distance above the apical
angle, with a spine-like hair. First segment of outer ramus
subquadrate, slightly narrower than the second basal seg-
ment, and about as wide as long ; second segment about as
wide as the first and twice as long, provided at the end of
the proximal third with a small bead-like tubercle. Mar-
ginal spine very large and strong, longer than the segment
itself, somewhat sinuously curved, and inserted near the
distal angle. Terminal hook very long, as long as the remain-
der of the right leg including the basal segments, but not
twice as long as the marginal spine ; very slightly recurved
at the tip and denticulate at the inner margin.

Inner ramus of the right fifth leg one-segmented, very
short, barely reaching the end of the first segment of the
outer ramus ; apex bluntly rounded and delicately hairy.

First segment of outer ramus of fifth foot of female (PI.
XXVII., Fig. 2) subquadrate, about twice as long as wide.
Second segment, or unguiform process, about as long as the
first, subcorneal or but slightly curved, delicately denticulate
on the inner margin. Third segment small but distinct, armed
with two spines, the inner of which is more than twice as
long as the outer, reaching about to the middle of the second
segment.

Inner ramus of fifth foot of female indistinctly two-seg-
mented, short, reaching just beyond the end of the first seg-
ment of the outer ramus ; apex bluntly triangular, armed
with a few short hairs, the innermost of which is longer than
the rest and spine-like.

Length of female 1.2 mm. ; of male 1.05 mm.

The material in Avhich the specimens described were found
was loaned me by Mr. Adolph Hempel, of Gotha, Florida,
and was collected by him in a series of Florida lakes from
January to March, 1896.

D. albuquerquensis is one of the few American species of
Diaptomus in which the inner ramus of the fifth leg of the
female is two-segmented. In some cases this ramus, instead
of being bluntly triangular, is acute, and reaches only to the
end of the first segment of the outer ramus. The first basal

North American Species of Diaptomus. 149

segment is sometimes armed at the outer distal angle with
a short, sharp spine.

Herrick (Herrick and Turner, '95) states that he found the
second segment of the left fifth leg of the male to be granular
on the inner margin, and the marginal spine of the right leg
denticulate on the inner margin and at the base. In both
these respects my specimens differ from his, the second seg-
ment of the left foot being hairy instead of granular, and
the marginal spine of the right foot perfectly smooth. Her-
rick's statement that "the first pair of antennae reach to the
extremity of the furca or surpass them" leads me to think
that they are longer in the Florida specimens than in his,
since they clearly reach beyond the tips of the f ureal setse in
every individual which I have examined.

In New Mexico Herrick found this species, in connection
with D. novamexicanus, in the water supply of the city of
Albuquerque; but in the Florida lakes it was found with
I). mississippiensis Marsh, the two forms being about equally
abundant. They are very much alike in general appearance,
but the males may be distinguished without dissection by the
antepenultimate article of the right antenna, which is armed
in D. albaquerquensis while it is unarmed in D. mississippien-
sis. Herrick gives the length of the female as 1.4-1.6 mm.,
but the largest female from Florida was 1.2 mm., while the
male was only 1.05 mm. in length, the average being con-
siderably smaller.

Diaptomus novamexicanus Herrick.

Diaptomus novomexicanus , Herrick, '95, p. 46, Fig. 27-29.
Diaptomus novamexicanus, Herrick and Turner, '95, p. 70, PI. VI.,
Fig. 7-10.

Among the smaller species of the genus, moderately robust.
Cephalothorax widest somewhat in front of the middle. Last
two thoracic segments distinct, the last armed on each side
with a small, short spine. First abdominal segment very
long, much exceeding the remainder of the abdomen, pro-
vided on each side with a short, sharp spine; second seg-
ment the shortest. Furcal rami equal in length to the

150 Illinois State Laboratory of Natural History.

preceding segment and about twice as long as wide; provided
with short apical setse.

Antennae of the female 2 5 -segmented, reaching to the base
or the end of the furca. Antepenultimate article of the right
male antenna armed with a lamina produced anteriorly into
an unguiform process which is shorter than the penultimate
article.

Outer ramus of the fifth pair of feet in the female obviously
three-segmented. Unguiform process of the second segment
arcuate, finely denticulate within and at the end, armed on
the outer margin near the base of the last segment with a
small spine. Last segment small but distinct and armed
with two short subequal spines.

Inner ramus of fifth foot of female one-segmented, as long
as the basal segment of the outer ramus ; apex ciliate and
armed with two subequal spines,

Left fifth leg of male reaching slightly beyond the end of
the first segment of the outer ramus of the right foot. First
basal segment armed on the outer margin with a short, sharp
spine. Second segment of the outer ramus oblong-ovate,
armed with two large spines ; inner margin delicately aculeate
toward the apex, and bearing a ciliate lamina.

Inner ramus of left fifth leg one-segmented, quite long,
reaching beyond the middle of the second segment of the
outer ramus ; hairy at the apex.

First basal segment of right fifth leg of male armed on the
outer margin with a rather long, sharp spine. First segment
of the outer ramus subquadrate, slightly longer than broad ;
second segment very long and narrow, more than twice as
long as the preceding segment. Marginal spine slender,
more than half as long as the segment itself, and inserted at
about the beginning of the distal third. Terminal hook long
and slightly curved.

Inner ramus of right fifth leg one-segmented, rather long,
reaching beyond the end of the first segment of the outer
ramus ; apex acute, minutely ciliate.

Length of female 1.1-1.2 mm.

North American Species of Diaptomus. 151

The above description is compiled from Herrick's first
paper on this species ('95) and from the figures and the
English and Latin descriptions in his later paper (Herrick
ai d Turner, '95). Both of these articles are published as
original descriptions, although there was nine months' differ-
ence in the time of their appearance.

Diaptomus oreg-onensis Lilljeborg. (PL XXIX., Fig.
1, 2.)

Diaptomus oregonensis, de Guerne et Richard. '89b, p. 53, PI. II., Fig.

5; PI. III.. Fig. 8.
Diaptomus oregonensis, Marsh, '93, p. 200, PI. IV., Fig. 4, 5.
Diax>tomus oregonensis, Marsh, '95, p. 8, PI. VII., Fig. 5.
Diaptomus oregonens is, Herrick and Turner, '95. p. 72, PI. IV., Fig.

7-12 ; PI. IX., Fig. 3.

A species of medium size. Cephalothorax widest about
the middle. The last two thoracic segments confluent above,
the last one, seen from above, slightly produced laterally,
bluntly rounded but unarmed ; in the male armed with two
very minute spines on each side. First abdominal segment
as long as the rest of the abdomen.* Third segment and
furcal rami subequal, the latter about one and a half times
as long as broad and delicately hairy within. In the male
the first abdominal segment is short and unarmed ; second
and third segments and furcal rami about equal ; fourth
segment the longest, about equal in length to the first two
segments taken together. Furcal rami about as in the female.

Antennae of the female 25 -segmented, extending beyond the
tips of the furcal seta?. Prehensile antenna of the male but
slightly swollen, the antepenultimate article entirely unarmed.

First basal segment of fifth leg of female (PI. XXIX., Fig.
2) with the usual delicate hair on the outer margin. First
segment of outer ramus about twice as long as wide, slightly
arcuate, margins parallel ; second segment about as long as
the first, moderately curved, terminating in an acute point,

*This segment hart a very peculiar appearance. Owing to the thicker anterior
part, the segment seemert to have a suture at about the middle, and this was so mis-
leading that I doubted if the specimens on the slides were really females until I could
see the antennae, and not until 1 could get a side view was I at all certain that there
was only one segment.

152 Illinois State Laboratory of Natural History.

very minutely hairy on the inner margin ; third segment
wanting, represented by two short spines, the inner twice as
long as the outer.

Inner ramus of fifth leg of female one-segmented, extend-
ing very slightly beyond the first segment of the outer ramus ;
apex obtuse, hairy, armed on the inner margin and at the
tip with two rather long subequal spines.

First basal segment of right fifth leg of male (PI. XXIX.,
Fig. 1) with a small tubercle on the outer margin; second
segment subquadrate, about one and a half times as long as
the first. First segment of the outer ramus subquadrate,
about as long as the first basal segment with overhanging
outer apical angle ; second segment slightly narrower than
the first, about twice as long as wide, with a small projection
at the middle of the inner margin. Marginal spine near the
apical angle, slender, with a slight angle about one fourth
its length from the base ; length about equal to the distance
between its base and the base of the segment. Terminal
hook long and slender, longer than the two preceding seg-
ments but not as long as those and the second basal segment ;
very minutely denticulate on the inner margin.

Inner ramus of right fifth leg one-segmented, extending to
a point about midway between the base of the second seg-
ment of the outer ramus and the projection on the inner
margin of this segment ; outer margin hairy ; apex bluntly
triangular and hairy.

Second basal segment of left fifth leg of male subquadrate,
about one and a half times as long as broad, slightly pro-
duced on the inner margin a short distance above the apical
angle. First segment of outer ramus slightly narrower than
the second basal segment and about twice as long as wide ;
outer margin moderately arcuate, the inner margin hairy.
Second segment produced into three digitiform processes :
the outermost blunt and .by far the longest ; the middle one
blunt, barely one fourth the length of the outer; and the last
very short, hardly more than a tubercle, with an acute apex
pointing straight inward. The segment is armed on the inner
margin with a hairy, cushion-like process.

North American Species of Diaptomus. 153

Inner ramus of left fifth leg somewhat spatulate, extend-
ing slightly beyond the end of the first segment of the outer
ramus ; inner margin hairy ; apex bluntly rounded and hairy.

Length of female 1.25 mm. ; of male 1.15 mm.

The above description is based on specimens found in col-
lections made in Lake Calhoun, Minn., in July, 1891, and
differs considerably from Lilljeborg's original description in
de Guerne and Richard's "Revision."

He gives the length of the female as about 1.5 mm. ; that
of the male, 1.4 mm.

I did not find in a single instance that the female had the
last thoracic segment armed with two minute spines on each
side, although they were present in the male. Lilljeborg does
not specify to which sex this part of his description applied,
but I assume that he followed the usual custom of referring to
the female unless especially stated otherwise.

The spines on the inner ramus of the female I found to be
on the inner instead of the outer margin, and they are so
figured by Marsh ('93).

In most cases I found but one spine representing the third
segment of the outer ramus of the fifth foot of the female,
while one specimen was found having one outer ramus as in
the type, the other with only one spine. I have thought it
best to make the description correspond to the type in this
particular, regarding the variation as local since Marsh ('93)
figures the two spines.

The inner ramus of the right fifth foot of the male in the
Minnesota specimens was longer than represented in the
original figures, and hairy on the inner margin and at the
apex. This hairiness is not mentioned in the original des-
cription and this ramus is figured smooth, while the inner
ramus of the left fifth foot, which is no more hairy than the
right, is hairy in the drawings.

In the left fifth foot of the male the first segment of the
outer ramus, although hairy, has not the definite cushion-like
process figured by Lilljeborg, and the outer two digitiform
processes of the second segment instead of being serrate
within are perfectly smooth. From Herrick's statement

154 Illinois State Laboratory of Natural History.

(Herrick and Turner, '95, p. 73) that "according to Richard's
drawing the spines are dentate," I judge that he also found
them smooth, since his own figures show them to be so.

This species was first found in 1888 at Portland, Oregon,
by Trybom, and described in 1889 byLilljeborg in de Guerne
and Richard's "Revision." Marsh says ('93) that it is the most
common form in central Wisconsin, being found quite gener-
ally in the shallower lakes, and that it occurs in the Great
Lakes, but not abundantly ('95). Herrick (Herrick and
Turner, '95) says that within the limits of Minnesota it had
been found only in Lake Minnetonka. I can now add Lake
Calhoun, Minn., and Sand Lake in northern Illinois.

Diaptomus siciloides Lilljeborg.

Diaptomus siciloides. tie Guerne et Richard, 'S9b, p. 54, PI. I., Fig.

7,8,28,32.
Maptomus siciloides, Herrick and Turner, '95, p. 69, PI. VIII.. Fig. 10.

"Among the smaller of this genus. The general form of the
body agrees almost exactly with that of D. gracilis Sars.
Cephalothorax slender, widest at the middle. The last two
thoracic segments confluent above. Lateral lobes of the
last one, seen from above, short and rounded, with rather
large mucros. First abdominal segment long, fully as long
as the remaining part of the abdomen (without the setae) ;
with distinct lateral processes at the anterior part, acuminate
and bending forward slightly. Furcal rami short, but fully
one and a half times as long as broad.

" First pair of antennae of the female, reflexed, surpass the
furca but do not reach the tips of the furcal setae ; composed
of 25 articles. Antepenultimate article of the prehensile
antenna of the male provided with a rather long hook-like
process reaching about to the middle of the penultimate
article.

"Fifth pair of feet in the female small but rather thick;
outer ramus biarticulate, hook-like process of second seg-
ment slightly curved, and almost equal to the first segment ;
the inner margin partly ciliate. Inner ramus simple, slightly
longer than the first segment of the outer ramus ; with a
small seta, slightly hairy at the apex.

North American Species of Didptomus. 155

" The inner margin of the first segment of the outer ramus
of the right fifth foot of the male dilated into a rather large
hyaline lamella. The second segment of this ramus moder-
ately curved, the outer margin ohtusely biangulate, the spine
placed below the middle. Claw simply curved. Inner ramus
small and slightly surpassing the middle of the first segment
of the outer ramus.

" The second segment of the outer ramus of the left fifth
foot almost triangular, with a beak-like spine and delicately
hairy within (intus tenai ore et subtiliter hispido); the apical
process obtuse, with a spine at the inner margin. Inner
ramus simple, sinuous, and reaching to or beyond the middle
of the second segment of the outer ramus.

"Length of female about 1.3 mm.; that of male slightly
less.

" Found in the month of May in Lake Tulare near the city
of Fresno, Cal., by G. Eisen.

"In the general form of the body this Diaptomus closely
resembles D, gracilis Sars as well as D. sicilis Forbes. It is
on account of this last resemblance that it was called siciloides.
It differs, however, from both : from D. gracilis in the shape of
the last thoracic segment and of the abdominal segments, of
the first pair of antennae, and of the fifth pair of feet ; from D.
sicilis in the shape of the fifth pair of feet, although this dif-
ference is not very great. It resembles D. sicilis more closely
than D. gracilis.

"It seems to live in great numbers in Lake Tulare near
Fresno, Cal. The female bears only four eggs."*

The statement concerning the number of eggs borne by the
female is erroneous, the number being variable, and appar-
ently dependent to a great degree on the temperature of the
water and on the food supply. In the high mountain lakes
from which the species was first described the statement
above quoted may hold true, but in the warm sluggish waters
of the Illinois Eiver, where food is abundant, the egg-sac is
very large, as many as eighteen eggs having been counted
on a single female. This is true also of specimens taken

*Lilljeborg*s description from de Guerne et Richard, 89b.

156 Illinois State Laboratory of Natural History.

from other localities, and no tendency toward constancy in
number of eggs for the same locality was made out.

The furcal rami in both sexes are hairy within, a point not
mentioned in the original description, although the rami are
so figured. All the specimens which I examined from the
various localities had this characteristic, although individuals
varied slightly in this particular.

As mentioned under the description of D. pallidus, D. sicl-
loidcs was the most abundant form found at Havana. It also
formed the greater part of the material from Spirit Lake,
Iowa, which was kindly loaned me by Prof. L. S. Ross, of
Drake University, Iowa.

The individuals taken from the Illinois River at Havana,
Illinois, in July and August, 1896, were all of an indefinite
color about like opalescent glass. The egg-sac in these was
blue, and there was a small pink spot near the eyes and just
behind them. These were the only specimens of slcllolcles
which I had opportunity to examine alive.

Diaptomus minutus Lilljeborg. (PI. XXX., Fig. 5-8.)

Diaptomus minutus, de Guerne et Richard, '89b, p. 50, PL I., Fig. 5,

6,14; PI. III., Fig. 25.
Diaptomus minutus, Marsh, '93, p. 199, PI. IV., Fig. 1-3.
Diaptomus minutus, Marsh, '95, p. S, Pi. VII., Fig. 3.

"Among the smallest of the genus. Body slender, widest
in front of the middle of the cephalothorax and at the pos-
terior part of the head. Fourth and fifth segments commonly
confluent above, sometimes in the adult specimen separated
by a suture; the lateral lobes, seen from above, short and
rounded, and provided with minute mucros. First abdomi-
nal segment of the female (PI. XXX., Fig. 8) about as long
as the remainder of the abdomen; rather dilated at its an-
terior part and rounded laterally ; furnished with very minute
spines. Second segment very short, third segment much
longer, and these segments indistinctly joined. Furcal rami
about twice as long as broad. Furcal setae unusually long.

"First pair of antennae of female somewhat surpass the
furca; composed of 25 segments. Antepenultimate article of

North American Species of Diaptomus. 157

the prehensile antenna of the male (PL XXX., Fig. 7) with a
slender process, long and straight, having a slight appearance
of an apical curve, and extending beyond the penultimate
article and sometimes almost reaching the end of the last
article.

"Setse of swimming feet unusually long. Outer ramus of
the fifth pair of feet in the female (PI. XXX., Fig. 5) In-
articulate; unguiform process of second article slightly
curved and minutely ciliate without. Inner ramus small
and almost rudimentary, with acuminate apex.

"Eight foot of the fifth pair of the male (PI. XXX., Fig. 6)
large but slender ; the second article of the outer ramus with
marginal spine minute and placed above the middle. Ter-
minal claw thick toward the base, rather short, and partly
minutely ciliate within. Inner ramus very small and quite
rudimentary.

"The left foot of the same pair very similar to that of J>.
siciloides and D. signicauda; the second article of the outer
ramus almost elliptical, the inner margin slightly emarginate
and partly ciliate at the lower part ; with a large and obtuse
apical spine and a smaller inner spine. Inner ramus simple,
attenuate toward the apex, and extending about to the middle
of the second article of the outer ramus.

"Length of female 1-1.1 mm ; of male hardly 1 mm.

"Found in Greenland, 61° 30'- G9° N. Lat., by Dr. C.
Nystrom and N. 0. Hoist, and at St. John's, Newfoundland,
by the former.

"This species is distinguished from others by its minute
size and by the fifth pair of feet. The female bears only two
eggs. D. minutus has been found in the Isle of Disko, north-
ern Greenland, but it seems to be more common in the
southern part. It is without doubt spread over the northern
part of North America, since it has also been found at St.
John's, Newfoundland."*

"We are able to confirm in every respect the description
given above by Professor Lilljeborg. We have, in fact, recog-
nized some rare specimens of D. minutus in a collection

*Lil]jeborg's description from deGuerne et Richard, 89b.

158 Illinois State Laboratory of Natwral History.

which M. Eiballier des Isles, French consul at Newfound-
land, was kind enough to make according to our directions
at Kinney's Pond near St. John's. This Calanid [centropa-
gid] was found in great numbers by M. Ch. Eabot in 1888
in the following localities in Greenland : Lake Egedesminde
(Bay of Disko) ; Godhavn ; near the glacier of Jakobshavn,
and in the Tasersuak of Julianehaab."*

"Marsh finds this form in Green Lake [Wisconsin], and
in the Great Lakes ; it may, therefore, be expected in Lake
Superior in Minnesota. "t

Marsh ('95) places sicilis var. imperfectus as a synonym
under minutus, but does it, as he says, "with considerable
hesitation." In looking over the drawings in the possession
of the State Laboratory I found some which had been repro-
duced but not published, and from these it was evident at a
glance that the var. imperfectus was not minutus but ashlandi,
although this was not evident from the description. A single
specimen of minutus was found among the collections from
Yellowstone Park, but it was so badly mutilated that no
drawings could be made from it.

Specimens from Greenland, kindly sent me by Professor
Lilljeborg, conform to his description but are somewhat
smaller than those figured by Marsh.

Diaptomus tryborni Lilljeborg. (PL XXXI., Fig. 1-5.)

lHaptomus trybomi, de Guerne et Richard, 'S9b, p. 58, PL I., Fig. 35;

PL II., Fig. 6; PL III., Fig. 14; PL IV., Fig. 28.
Diaptomus trybomi, Herrick and Turner, '95, p. 57, PL VIII., Fig. 17;

PI. IX., Fig. 4: PL X., Fig. 13.

" Of medium size. Cephalothorax widest about the middle.
Last two segments distinctly separated, and the last, seen
from above (PL XXXI., Fig. 3), slightly produced laterally,
provided with two spines (one of them minute) on each
side. Besides this the right part of this segment (PL XXXI.,
Fig. 2) bears a large dorsal appendage, triangular in form,
with mucronate apex, and extending toward the right. The

*de Guerne et Richard, 89b.

t Herrick. From Uerriek and Turner, '95.

North American Species of Diaptomus. 159

first caudal segment of the female is very characteristic of the
species (in the male it is of the ordinary form) and, unlike
that of D. signicauda, surpasses in length the rest of the
abdomen. This segment is provided at the anterior part on
both sides with a short and mucronate lateral process, and at
the posterior part with a large triangular process extending
almost directly toward the right, with apex slightly acumi-
nate. F ureal rami rather short, not twice as long as broad.

" First pair of female antennae 25 -segmented, almost reach-
ing the base of the furca. The antepenultimate article of the
prehensile male antenna (PI. XXXI., Fig. 1) armed with an
almost straight and rather slender process reaching almost
to the middle of the penultimate article, and provided with-
out with small teeth.

" Outer ramus of the fifth pair of feet in the female (PL
XXXI., Fig. 5) two-segmented; the unguiform process of the
second segment slightly curved, robust, moderately ciliate
within and at the middle part, last cilium broad, spine-like.
Third segment wanting, produced into two short spines, the
outer half as long as the inner.

"Inner ramus one-segmented, almost equal to the first seg-
ment of the outer ramus ; apex obliquely acuminate, pro-
vided with two rather long subequal spines.

" Second segment of the outer ramus of the right fifth foot
of the male (PI. XXXI. , Fig. 4) very long, longer than the
first segment and the basal segment taken together. Margi-
nal spine of this segment inserted above the middle. Termi-
nal hook slightly curved, inner margin ciliate.

" Inner ramus curved, ovate, broad, pointing inward, with
mucronate apex, barely reaching to the end of the first seg-
ment of the outer ramus.

" First and second segments of the outer ramus of the
left foot ciliate within, the second one obovate, hirsute toward
the apex, and bearing two short spines one of which points
inward.

" Inner ramus one-segmented, slender, equal to the first
segment of the outer ramus."

"Length of female about 1.5 mm. ; of male 1.4 mm.

160 Illinois State Laboratory of Natural History.

"This species, so remarkable from the peculiarities pre-
sented by the last thoracic and the first abdominal segments,
was found by the Swedish naturalist, Trybom, at Multrooma
Falls, Oregon."

The above is the description as given by Dr. Lilljeborg
(de Guerne et Richard, '89b). It agrees with the specimens
sent me by himself, but I note a few additional details.

The abdomen of the female, seen from above, is asymmet-
rical, as is also the last thoracic segment. The first abdom-
inal segment is dilated anteriorly, and posteriorly is produced
on the right to form a blunt, almost semicircular, process.
Seen from the side this is fin-shaped, and both this process
and the one on the last thoracic segment are penetrated by
muscles. The furcal rami are hairy within.

In the male the peculiar form of the right inner ramus,
the extreme shortness of the left leg, and the very irregular
shape of its last segment are especially characteristic. The
spines on the first basal segment of each leg and the teeth
on the terminal segment of the right leg are also conspicuous
because of their great size.

The peculiarity of a dorsal process is found, to my knowl-
edge, in but two other species: D. sanguineus Forbes, and D.
signieauda Lilljeborg. In the small size of the inner ramus
of the right fifth foot of the male, D. trybomi approaches the
male of D. sanguineus Forbes, D. minutus Lillj., and D. lin-
toni Forbes.

De Guerne and Richard give Multrooma Falls as the
locality, which was probably intended for Multnomah Falls,
Oregon, although Prof. Lilljeborg in a personal letter also
gives the former spelling.

Diaptomus franciscanus Lilljeborg. (PI. XXX.,Fig.l-4.)

Diaptomus franciscanus, de Guerne et Richard, *89b, p. 45, PI. I.,

Fig. 12, 13, 34; PI. III., Fig. 23.
DiapUxmus franciscanus, Ilerriek and Turner, *95, p. 5S, PI. VIII.,

Fig. 12. 1G.

"Larger and more robust than Diaptomus tyrreli. Cepha-
lothorax widest in the middle, and the last two segments
confluent above. Lateral lobes of the last thoracic segment

North American Species of Diaptomus. 161

seen from above, short and obtuse posteriorly ; armed with
small spines. First abdominal segment (PL XXX., Fig. 1)
about equal to the rest of the abdomen, moderately dilated
anteriorly, rounded at the sides, and armed here with small
spines or mucros ; always destitute of all lateral processes.
An imperfect suture remains long after maturity in the pos-
terior part of this segment. Second segment of the abdomen
much shorter than the third, and also more slender and
easily pushed within the preceding joint.* Furcal rami short,
fully one and a half times longer than broad ; sparsely ciliate
within.

"First pair of antennae of female, reflexed, extend about
to the furca ; composed of 25 articles. Antepenultimate
article of the male prehensile antenna (PI. XXX., Fig. 2)
provided with an unguiform process, slightly surpassing the
end of the penultimate article.

"Outer ramus of the fifth pair of feet in the female (PL
XXX., Fig. 4) three-segmented, the third segment very small
but distinct, and bearing two spines. The unguiform process
of the second segment of this ramus rather arcuate and finely
ciliate within at the lower part, the last spine thicker than
the rest. Inner ramus simple and equal to the first segment
of the outer ramus, bearing two long equal spines at the
apex, of which the outer is ciliate within at the base.

"The right fifth foot of the male (PL XXX., Fig. 3) rather
robust. The second segment of the outer ramus almost rect-
angular and comparatively short ; the outer marginal spine
placed near the apex, and the inner margin armed with a mi-
nute spine. Terminal hook long, distinctly sigmoid or S-
shaped and tapering toward the apex. Inner ramus small
and barely reaching the middle of the second article of the
outer ramus ; either imperfectly two-segmented or one-
segmented and armed with an apical spine.

"The second segment of the outer ramus .of the left fifth
foot of the male lamelliform, almost triangular, and thinner
within. This segment on the thicker, outer, side bears a short

* The meaning of the original at this point is rather obscure. It reads: "Seg-
mentum 2-dum caudcE 3-tio multo brevius ejusque testa tenuior et facile adstrtn-
genda."

162 Illinois State Laboratory of Natural History.

spine in the middle, and ends in a short obtuse process, the
inner apical angle of which exhibits three small oblique in-
cisions. The inner margin is minutely ciliate. The inner
ramus is simple and slender, attenuate toward the apex, and
reaching about to the middle of the second segment of the
outer ramus.

"Length of female, 2.3 mm. ; of male, 2.0 mm.

"Found near San Francisco by G. Eisen.

"This Diaptomus approaches IX. longicornis var. similis
Herrick in the shape of the body and of the lateral lobes of
the last thoracic segment, but it differs greatly in respect to
the fifth pair of feet, especially in the male. It seems to be
common in the vicinity of San Francisco, hence the name,
franeiscanus."*

The female is conspicuous chiefly for the extremely long
spines with which the inner rami of the fifth pair of feet are
armed. These are about as long as the ramus itself and
hairy at the base. The thorax and abdomen are of ordinary
form. The furca are hairy within, and also, but more
sparsely, on the outer margin. In the male the outer margin
is not hairy.

The outer ramus of the left fifth foot of the male is termi-
nated by a peculiarly flattened segment (PI. XXX., Fig. 3).
In a male of this species sent me by Professor Lilljeborg,
both inner rami of the fifth pair of legs are two-segmented.

Diaptomus eiseni Lilljebokg.

Diaptomus eiseni, de Guerne et Richard, '89b, p. 44, PI. I., Fig. 19,

29, 33.f
Diaptomus eiseni, Herrick and Turner, '95, p. 58, PI. X., Fig. 11.

"Among the largest of the genus. Cephalothorax widest at
the posterior part of the head. The last two thoracic seg-
ments usually confluent above or indistinctly segmented, and
the lateral lobes of the last segment, seen from above, short

*Lilljeborg's description and remarks from de Guerne et Richard, '89b.

t Confusion maybe caused by a slight mistake which crept into de Guerne and
Richard's "Revision." In the index and under the species names. Fig. id. PI. I. is
given as the fifth foot of D- zerricornis and also of D- eiseni. The "explanation of
plates' however, gives Fig. 29, PI. I., as that of I). eiseni, which by comparison with
the description is found to be correct.

North American Species of Diaptomus. 163

in the female; upper posterior angle rather acute, lateral
angle very obtuse, the spines of both angles thick and short.
First abdominal segment slightly longer than the remainder of
the abdomen (setae excepted), produced anteriorly into a rather
large lateral process with spines pointing obliquely backward.
Second abdominal segment very short. -Furcal rami short ;
sparsely hairy ; about one and a half times as long as broad.

"First pair of antennae reach to the lateral processes of the
first abdominal segment; composed of 25 segments. Ante-
penultimate article of the prehensile antenna of the male
with a long curved and acuminate process almost surpassing
the end of the antenna.

"Outer ramus of the first pair of feet, especially in the
female, pectinately setose.

"Outer ramus of the fifth pair of feet in the female two-
segmented, the second segment with large unguiform process
within and heavily spined without. The inner ramus of this
foot rather long, clearly not reaching the end of the first seg-
ment of the outer ramus ; suture sharply indicated ; pro-
vided at the apex with two spine-like setae and within with
minute spines.

"Eight fifth foot of the male rather robust. Second basal
segment dilated within into a rugose lamella ; second segment
of the outer ramus with marginal spine placed near the apex.
Inner margin of terminal claw slightly sigmoid; from the
middle toward the apex first delicately pectinately spined,
and thence tuberculate. Inner ramus small and indistinctly
two-segmented, extending slightly beyond the middle of the
second segment of the outer ramus; armed at the apex with
a spine, and at the same place and within with thick cilia.

"Left foot of the fifth pair of the male much smaller than
the right. Second or last segment of the outer ramus of this
foot with the apex narrowed but obtuse, and within this an
acuminate spine ; an emarginate narrow and hairy lamina
on the inner margin. Inner ramus slender, rather long, and
notably surpassing the middle of the second segment of the
outer ramus ; indistinctly two-segmented, the apex similar
to that of the right inner ramus.

164 Illinois State Laboratory of Natural History.

"Length of female, 4 mm. ; of male, 3.5 mm.

"Found, near Fresno, Cal., by G. Eisen, the Swedish zoolo-
gist, member of the San Francisco Scientific Academy."

"This Diaptomus is dedicated to Mr. G. Eisen, who found
it in California with a great number of other Entomostraca.
It was given by him to the Zoological Museum of the Uni-
versity of Upsala. D. eiseni is very distinct from all the
American species described by Profs. Forbes and Herrick."*

The last thoracic segment of the female is strongly pro-
duced posteriorly and the first abdominal segment is moder-
ately dilated and armed on each side with a large spine.
This form may also be recognized on account of its great
size, being but little smaller than D. stagnalis or D. shoshone
Forbes. The fifth pair of legs are remarkable for the ex-
treme size of the inner of the two spines representing
the third segment of the outer ramus, which is made still
more striking by a row of strong teeth on each margin. The
second segment of the outer ramus is also armed with strong
teeth on the inner margin.

The fifth pair of legs of the male may be easily recognized
from the fact that at least an indication of a suture is found
on each inner ramus, making it indistinctly two-segmented.
The rugose lamella on the second basal segment of the right
fifth leg is also very characteristic.

Diaptomus signicauda Lilljeborg. (PI. XXIX., Fig. 3-6.)

Diaptomus signicauda, de Guerne et Richard, 'S9b, p. 55, PI. I., Fig.

15,10,31; PI. III., Fig. 22.
Diaptomus signicaudatus, Herrick and Turner, '95, p. 63, PI. VIII.,

Fig. 13; PI. IX., Fig. 10.

"This species is among the smaller species of this genus.
Form of the body very slender. Cephalothorax widest in front
of the middle, at the second segment. Last two segments of
the thorax (PI. XXIX., Fig. 6) confluent above, the last, seen
from above, with rather large and projecting lateral lobes,
posterior angles acute, with small spines. Fourth thoracic
segment, seen from the side, provided above with a small

*Lilljeborg's description and remarks from de Guerne et Richard. 'S9b.

North American Species of Diaptomus. 165

hump. First abdominal segment of the female very char-
acteristic of the species, giving to it its name. This seg-
ment is provided at the anterior part with short, mucronate
lateral processes, and at the posterior part on the right side
with a large process bent obliquely backward and moderately
acuminate. Besides this an indication of a suture is also
often present. The length of this segment, posterior process
excepted, is slightly less than the remainder of the abdomen.
Furcal rami hardly more than half as long as broad.

"First pair of antennae of the female always 25-segmented;
reflexed, slightly surpass the furcal rami, but do not reach
the end of the furcal setae. The antepenultimate article of
the prehensile antenna of the male (PI. XXIX., Fig. 4) armed
with a medium-sized hook-like process.

"Fifth pair of feet of female (PL XXIX., Fig. 5) very simi-
lar to the corresponding pair of I), siciloides. Outer ramus
two-segmented; unguiform process of the second segment
slightly curved, almost parallel with the first article ; very deli-
cately ciliate within, the last cilia thicker and spine-like.

"Inner ramus one-segmented, longer than the first seg-
ment of the outer ramus ; apex obliquely acuminate and
ciliate, and bearing two equal ciliate spines.

"The right fifth foot of the male (PI. XXIX., Fig. 3) rather
slender. First segment of the outer ramus dilated within
into a small hyaline lamina. The second segment as long as
the first article and the second basal segment together. The
marginal spine of the second segment is situated a little
below the middle. Terminal hook simply curved.

"Inner ramus rather broad, acuminate, and short, not
reaching to the end of the first segment of the outer ramus.

' The second segment of the outer ramus of the left foot
elliptical or oblong-ovate ; within and toward the apex very
delicately aculeate, and bearing two large spines, one of
which inclines inward.

" Inner ramus simple and slender, but long, and extending
beyond the middle of the second segment of the outer ramus.

"Length of female about 1.5 mm. ; of male, 1.3 mm.

166 Illinois State Laboratory of Natural History.

"Found in the Sierra Nevada Mountains, California, at a
height of from 8,000-10,000 feet above sea-level by G.
Eisen. Appears to be very common in small pools in this
locality.

" This Diaptomus is very distinct from all known species
on account of the peculiar form of the first abdominal seg-
ment. In this respect it approaches I), roubaui Richard, and
the genus Epischura Forbes. In the case of these Copepoda,
however, it is the male which is distinguished by the irregu-
larity of the abdomen. The name which I have given it
refers particularly to the shape of the female abdomen."*

There is nothing to add to the above description of this
species except that the furca are delicately hairy within, a fact
neither shown in the drawings nor mentioned in the original
description. The last thoracic segment of the female is
strongly produced, and the first abdominal segment greatly
dilated at its anterior part. The process on the first abdomi-
nal segment is even larger in some cases than represented in
the original drawings.

In the male also the last thoracic segment is produced, but
not so much as in the other sex. The fifth pair of legs are
very similar to those of D. sieiloides, from which they may be
distinguished by the shape of the right inner ramus and of
the hyaline lamina on the first segment of the outer ramus of
the right fifth leg. Both inner rami are delicately hairy, but
I fail to find the smooth, cushion-like process on the outer
margin and at the base of the left inner ramus which is fig-
ured in the original drawings but of which no mention is
made in the text.

The females of D. signicauda and D. trybomi both have a
"dorsal process," and in this respect approach D. sanguineus
Forbes.

Individuals of this species were kindly sent me by Dr.
Lilljeborg, but were unavoidably delayed until after this
description was completed. There was no time to rewrite it,
hence these remarks are in the form of addenda. The same
is true of trybomi, eiseni, and franciscanus.

*Lilljeborg's description and remarks from de Guerne et Richard, '89b.

North American Species of Diaptomus. 167

Diaptomus ashlandi Marsh. (PI. XXXII., Fig. 1-4.)

Diaptomus sicilis var. imperfectus, Forbes '90, p. 703.
Diaptonms ashlandi, Marsh, '93, p. 198, PI. III., Fig. 11-13.
Diaptomus ashlandi, Herrick and Turner, '95, p. 60, PI. VI., Fig. 4-6.
Diaptomus ashlandi, Marsh, '95, p. 7, PI. VII., Fig. 2.

A small, slender species, about the same width throughout.
Suture between head and thorax distinct. Last two thoracic
segments distinct, the last one strongly bifid and armed on
each side with a small blunt spine. Abdomen long and
narrow ; inclusive of the f urea, about half as long as the ceph-
alothorax. First abdominal segment as long as the remainder
of the abdomen exclusive of the furcalrami ; dilated laterally ;
with a small spine on each side (unarmed in the male). Second
and third segments subequal. Furcal rami barely twice as
long as wide ; hairy within.

Antennae 2 5 -segmented, reaching to the base of the furcal
rami or slightly beyond. Prehensile antenna (PI. XXXII.,
Fig. 4) moderately swollen; segments 19, 20, and 21, and
22 and 23, ankylosed ; process on the antepenultimate seg-
ment extending almost to the middle of the last segment, the
end knobbed and roughened or tuberculate at the inner
margin.

Fifth pair of legs of the male (PL XXXIL, Fig. 3) rather
slender ; left leg reaching about to the end of the first seg-
ment of the outer ramus of the right leg. On the anterior
surface of the first basal segment of the right leg is a large
tubercle bearing at the tip a small acute spine. Second
basal segment without special characteristics. First seg-
ment of the outer ramus subquadrate, slightly broader than
long ; inner apical angle somewhat produced, the process
ending in an acute point. Second segment about three times
as long as the first, with a sharp angle at end of proximal
third, from the point of which springs the lateral spine. This
is about half as long as the segment, with an angle near its
base. Terminal hook long and slender, rather more robust
than that of D. sicilis Forbes, but shaped very much like it;
minutely denticulate on the inner margin.

168 Illinois State Laboratory of Natural Histor/i.

Inner ramus of right fifth leg one-segmented, very narrow,
extending about half its length beyond the end of the first
segment of the outer ramus ; apex with an acute triangle,
hairy at the tip ; sides parallel.

First basal segment of the left fifth leg produced on the
anterior aspect, near the outer margin, into a long tubercle
ending in a minute, sharp spine ; second basal segment with
delicate hair near the outer distal angle. First segment of
the outer ramus subquadrate, shorter than the preceding,
slightly longer than broad ; second segment about as long as
the first and about twice as long as wide ; very similar to the
corresponding segment of D. sicilis Forbes.

Inner ramus of left fifth leg long and narrow, margins sin-
uously curved; extending about to the middle of the last
segment of the outer ramus ; delicately hairy at the tip.

Second basal segment of fifth leg of female (PI. XXXII.,
Fig. 1, 2) with the usual delicate hair at the outer margin.
First segment of the outer ramus about twice as long as
wide ; second segment somewhat longer than the first, taper-
ing to a rather sharp point and curving outward slightly,
delicately denticulate on the inner margin; third segment
wanting, represented by two spines, the outer about twice as
long as the inner.

Inner ramus one-segmented, extending slightly beyond
first segment of the outer ramus, hairy, ending in acute tri-
angular tip ; armed at the apex with two rather long sub-
equal spines which are sometimes hairy.

Length of female .97 mm. ; of male .9 mm.

A reference to the "Distribution of American Species" (see
page 183), will show the wide range of this form. In the
collections of the U. S. Fish Commission from Lake Samma-
mish, Lake Union, and Lake Washington, "Wash. ; Tsiltcoos
Lake, Tahkenitch Lake, and Klamath Lake, Oregon ; and
Lake Pend d' Oreille and Gamble's Lake, Idaho, T>. ashlandi
was found in immense numbers, being either the only centro-
pagid or occurring in connection with Epischura nevadensis
Lilljeborg.

North American Species of Diaptomus. 169

Diaptomus ashlandi is very similar to D. sicilis Forbes and
hardly to be distinguished from it but for a slight difference
in the last segment of the left fifth foot of the male and the
position of the marginal spine of the right fifth foot. In the
Laboratory collections from Yellowstone Park and the Flat-
head region of Montana forms occur which seem to be inter-
mediate between the two, and it was exceedingly difficult to
decide to which, if either, of the two species they belonged.
D. ashlandi seems to me, however, to be a good species, since
the form, as described by Marsh ('93 and '95) and as found
by myself in other collections, exhibits constant, though some-
what minute, differences from sicilis hard to describe, but at
once evident from the figures.

A very peculiar modification of the inner ramus of the fifth
foot of the female was noted in a specimen taken from an
alkaline pond in Yellowstone Park. In this individual one of
the feet (PI. XXXII., Fig. 1) was normal in every respect,
while the inner ramus of the other was armed on its outer
margin, at the end of the proximal third, with a sharp, smooth
spine about half as long as the ramus itself.

D. sicilis var. imperfect us Forbes ('90) is here made a syn-
onym of D. ashlandi, because unpublished Laboratory draw-
ings of that variety clearly show it to be such. Marsh's de-
scription must stand, since the description of imperfectus was
not complete enough to identify the form. This species was
also noticed by Dr. Forbes in the collections reported on in
'93, but was erroneously regarded by him as an immature
form of D. sicilis.

Diaptomus reighardi Marsh. (PI. XXVIII. , Fig. 1.)

Diaptomus reighardi, Marsh, '95, p. 9, PI. I., Fig. 1-4.

A medium-sized species ; body about the same width
throughout. Sutures between the first and second, and between
the last two, thoracic segments distinct ; last thoracic seg-
ment not produced, armed on each side with a very minute
spine. First abdominal segment almost as long as the rest
of the abdomen, dilated laterally, armed on each side with a

170 Illinois State Laboratory of Natural History.

minute spine ; second and third segments subequal ; furcal
rami slightly longer than the third segment, about twice as
long as wide ; and delicately hairy within. In the male the
second abdominal segment and the furcal rami are subequal,
and each is longer than any of the other segments. The
furcal rami are considerably longer than the preceding seg-
ment, fully twice as long as wide, and hairy within.

Antennae 2 5 -segmented, reaching well beyond the tips of
the furcal setae. Right male antenna not much swollen
anterior to the geniculate joint • antepenultimate segment
unarmed.

Left fifth leg of male (PL XXVIII., Fig. 1) short, extending
beyond the middle, but not reaching the end of the second
segment, of the outer ramus of the right leg. First basal
segment armed at the outer distal angle with a short, sharp
spine. Second basal segment about equal to the first, almost
as wide as long. First segment of the outer ramus irregularly
trapezoidal in form, about half as wide as the second basal
segment, and delicately hairy on the inner margin. Second
segment somewhat as in D. oregonensis Lilljeborg. It is pro-
duced into two digitiform processes, the outer of which is
more than twice as long as the inner and armed on the inner
margin at the tip, with a small cushion-like, delicately hairy
process. There is a distinct suture between the main part of
the second segment and the inner of the two processes, and the
process itself is minutely denticulate on the outer margin.

Inner ramus of left fifth leg one-segmented, reaching to the
base of the inner digitiform process ; outer margin hairy,
almost straight ; inner margin somewhat sinuously curved.

First basal segment of the right fifth foot of the male sub-
quadrate, slightly longer than wide, armed at the outer distal
angle with a short, sharp spine. Second segment about as
wide as the first and one and a half times as long ; provided
with the usual hair on the outer margin. First segment of the
outer ramus a little more than half as long as the second
basal segment and slightly longer than wide ; second segment
less than half as wide as long and more than twice as long as
the preceding segment. Marginal spine rather short, about

North American Species of Diaptomus. 171

as long as the segment is wide ; inserted near the beginning
of the distal third ; slightly curved and distinctly denticulate
on the inner margin. Terminal hook rather slender, a little
more than twice as long as the preceding segment ; not regu-
larly curved, but divided approximately into thirds by abrupt
angles, the upper one very sharp, below which on the inner
margin, the hook is delicately but distinctly denticulate.

Inner ramus of right fifth foot short, one-segmented, reach-
ing just to, or extending very slightly beyond, the end of the
first segment of the outer ramus ; apex bluntly triangular and
delicately hairy.

First segment of the outer ramus of the fifth leg of the
female subquadrate, about twice as long as wide ; second seg-
ment slightly shorter than the first, moderately curved, the
inner margin distinctly denticulate ; third segment wanting,
being represented by two spines ; the outer short and thick
and only about half as long as the inner.

Inner ramus of fifth leg of female, one-segmented, extending
slightly beyond the end of the first segment of the outer ramus ;
delicately hairy at the apex and on the distal fourth, and
armed in addition to this with two slender spines about as long
as the shorter of the two representing the third segment of
the outer ramus.

Length of female, 1.1395 mm.; of male, 1.0248 mm.

The above measurements are those of Professor Marsh.
The largest female I examined was 1.13 mm. in length, the
smallest, 1 mm. ; while the largest male I measured was 1
mm. in length, the smallest, .96 mm.

Prof. Marsh originally described this species, and I am
greatly indebted to him for the specimens from which the
above description was made. He found D. reighardi in only
three localities, all in Michigan ; North Lake, on Beaver
Island, Intermediate Lake, and Crooked Lake. I do not
know of its having been recorded from any other place.

At first sight D. reighardi, in respect to the fifth pair of
legs of the male, is very like D. oregonensis Lilljeborg, but
the details of structure are very different in the two, and there
can be no doubt as to the validity of the species.

172 Illinois State Laboratory of Natural History.

Diaptomus birgei Marsh.

Diaptomus birgei, Marsh,'94, p. 16, PI. I., Fig. 4-6.
Diaptomus birgei, Herrick and Turner, *95, p. 79, PI. XLVIL, Fig.
4-6.

" Of moderate size. The first segment of the cephalothorax
is nearly equal in length to the three following. The first
segment of the abdomen of the female is as long as the
remainder of the abdomen and the furca. It is much dilated
in front. The second segment is nearly twice as long as the
third, and about equal in length to the furca. The second
and third joints are very closely united.

"The antennse extend to the end of the furca. The right
antenna of the male is much swollen anterior to the geniculat-
ing joint; the antepenultimate joint is produced on its distal
end into a short, blunt process, which makes very nearly a
right angle with the longitudinal axis of the joint.

"The outer ramus of the fifth foot of the female is two-
jointed, the third joint being represented by two spines. The
inner ramus is one- jointed, hardly as long as the first joint
of the outer ramus, and armed at the tip with minute setae
and two rather long spines.

" The basal joint of the right fifth foot of the male is elon-
gated, trapezoidal in form, its greatest breadth being at its
distal extremity. The first joint of the outer ramus is broader
than long, armed on its inner margin with a broad, thin ex-
pansion of the integument. The second joint is elongate,
broader at base; the lateral spine is situated at about the
middle of its length, is long and stout, and armed on its inner
margin with fine serrulations. The terminal hook is slightly
angular, and armed with fine serrulations on its inner mar-
gin. The inner ramus is one-jointed, equaling in length the
first joint of the outer ramus.

" The left fifth foot of the male reaches slightly beyond the
first joint of the outer ramus of the right. The basal joint is
quadrangular, considerably shorter than the right basal joint.
The first joint of the outer ramus is about twice as long as
broad. The second joint is slightly longer than the first joint ;
it is expanded at base, where it is armed with fine hairs, and

North American Species of Diaptomus. 173

terminates in a finger-like process bearing a falciform spine.
The inner ramus extends to about one half the length of the
second joint.

"Length of female, 1.5 mm.; of male, 1.3 mm."*

Marsh states, in connection with the original description,
that the material in which this species was found — collected
by Professor Birge at New Lisbon, Wisconsin — contained only
a few individuals, and that his own search for it in other
Wisconsin localities had been unsuccessful. He says also
that the species resembles the European species D. gracilis
more closely than any other American form.

The description quoted above is the only literature on the
subject, and while a request for slides or specimens of the
species by Professor Marsh was kindly complied with in the
case of most of his species, to his own as well as my regret
he was unable to let me have either slides or specimens of D.
birgei.

Unfortunately, as Marsh says, but few specimens were found,
and further study of the species must consequently be deferred
until later collections shall afford an opportunity.

Diaptomus mississippiensis Marsh. (PI. XXXIII., Fig.
1-4.)

Diaptomus mississippiensis, Marsh, "94. p. 15, PJ. I., Fig. 1-3.
Diaptomus mississippiensis, Herrick and Turner, '95, p. 78, PI.
XLVIL, Fig. 1-3.

A medium-sized species. Body slender, widest about the
middle of the posterior third, the male a little more slender
than the female, and the widest part slightly farther forward.
Last two cephalothoraic segments indistinctly confluent ;
suture between the first two distinct. Last cephalothoracic
segment, seen from above, not produced, but bearing a
minute obtuse spine pointing backward ; seen from the side
it is broadly rounded, with the spine in the middle, giving it
the form of a brace ( — ■— ^). First abdominal segment about
as long as the remainder of the abdomen (PI. XXXIII. , Fig.
4), with a short obtuse spine opposite the anterior margin of

♦Description quoted from Marsh, "94.

174 Illinois State Laboratory of Xatural History.

the receptaculum seminis ; the second segment the shortest ;
third segment slightly longer than the second. In the male
(PI. XXXIII., Fig. 1) there is little difference in the length
of the abdominal segments. Furcal rami broad, but little
longer than the third abdominal segment; distinctly hairy
within. Furcal setae thick at the base, tapering gradually
toward the tip ; distinctly setose. The inner furcal seta is
smooth in both sexes.

Antennae 2 5 -segmented, reaching to or slightly beyond the
tips of the furcal setae. The right male antenna with the six
segments preceding the geniculation greatly swollen ; ante-
penultimate article unarmed; segments 19, 20, and 21, also
22 and 23 ankylosed.

Fifth pair of feet of the female (PL XXXIIL, Fig. 2) of
moderate size. First basal segment trapezoidal, the longer
base forming the inner margin. Second segment of the outer
ramus long, narrow, acuminate, shorter than the preceding
segment, perfectly smooth within. Third segment wanting ;
represented by two straight and pointed spines, an inner short
one and an outer one more than twice as long.

Inner ramus of fifth foot of female one- segmented, reach-
ing almost to the middle of the second segment of the outer
ramus; distinctly hairy on inner margin near the apex, where
it is armed with two spines, the inner one being fully one
third as long as the ramus itself.

First segment of outer ramus of right fifth foot of male
(PL XXXIIL, Fig. 3) subquadrate, slightly longer than broad,
the second segment nearly twice as long as the first, its upper
half about as wide as the first. A little below the middle of
this segment the inner margin is produced into a short spine-
like process, concave toward the apex of the segment. Be-
tween this and the apex the segment is produced into a
narrow, triangular hyaline lamina, tapering from the broad
upper part to the inner apical angle. Marginal spine long
and curved, concave toward the apex of the segment and
inserted very near the outer apical angle. Terminal hook
long and very slender, with two sharp angles dividing it
approximately into thirds ; upper third rather thick as

North American Species of Diaptomus. 175

compared with the remainder; lower two thirds very minutely
spinose ; tip sometimes slightly recurved.

Inner ramus of right fifth foot one-segmented, narrowing
but slightly toward the tip. It reaches almost to the middle
of the last segment of the outer ramus, but not to the hook-
like process. Apex rounded ; unarmed or very delicately
hairy.

Outer ramus of the left fifth foot two-segmented. First
segment irregularly trapezoidal ; small and inconspicuous,
with a delicately hairy cushion-like process on the inner mar-
gin. Last segment consisting of two digitiform processes,
forming a forcipate structure. Seen from behind, the upper
process is smooth, the base slightly swollen. It is a little longer
than the other and about one and a half times as long as the
preceding segment, tapering gradually from the thickened
part to an obtuse point. The lower process (seen from behind)
is about equally broad at the base and at the beginning of the
last third, whence it narrows quite suddenly to form an obtuse
point. It is provided within and at the apex with four or
five small teeth.

Inner ramus of left fifth foot paddle- shaped, considerably
broadest at the apex ; reaching almost to the tip of the outer
ramus ; either smooth or very delicately hairy.

Length of female, 1.2 mm. ; of male, 1.1 mm.

Most of the specimens examined were taken from Lake
Maitland, Florida, from material kindly loaned me by Mr.
Adolph Hempel.

The above was prepared as a description of a new species,
but when I saw Professor Marsh's slides there was no longer
any doubt as to the identity of mississippiensis and this Florida
form. Prof. Marsh ('94) figures the furca of the female as
perfectly smooth within, while in all of the specimens from
Florida, as well as in those which he kindly loaned me, they
are distinctly, though not heavily, setose within. The inner
rami of the fifth pair of feet in the male, however, differ con-
siderably — probably a varietal difference, since in a few of my
specimens they approached the form shown in his figures.
In the Florida specimens I fail to find the asymmetry in the

176 Illinois State Laboratory of Natural History.

abdominal spine mentioned by Marsh, but since the speci-
mens from the two localities differ in other respects it is not
unlikely that this difference also may exist.

Found by Professor Marsh in collections from small lakes
and ponds in Mississippi, and by the writer in material col-
lected from a number of Florida lakes in March, 1896, by
Mr. Adolph Hempel. Professor Marsh states that in collec-
tions made in Mississippi in January and February, 1893,
D. mississippiensis was the only Diaptomus found ; but in the
Florida collections this species occurred in connection with
D. albuquerquensis Herrick, the two being about equal in
numbers. In general appearance these two species are very
similar, but they are widely different in the details of their
structure.

Diaptomus tyrrelli Poppe.

Diaptomus tyrrelli, Poppe, '88, p. 159.

Diaptomus tyrrelli, de Guerne et Richard, '89b, p. 39, PI. I., Fig.

17,18; PI. IV., Fig. 26.
Diaptomus fresnanus, Lilljeborg, in litt*
Diaptomus tyrrelli, Herrick and Turner, '95, p. 76, PI. X., Fig. 9.

"Of medium size. Cephalothorax widest at the middle
and at the lateral lobes of the last segment. Last two tho-
racic segments confluent above, and the last, seen from above,
produced obliquely into large lateral processes, almost ovate,
acuminate posteriorly, with a rather large mucro. First
abdominal segment almost as long as the rest of the abdomen,
somewhat dilated anteriorly, and provided with long mucro-
nate lateral processes. Second and third abdominal segments
rather short, with a vestige of a transverse suture anteriorly.
Furcal rami short, sparsely hairy, and almost one and a half
times as long as broad.

"First pair of antennae in the female, reflexed, reach
almost to, sometimes to the end of, the furca ; composed of
twenty-five segments. Antepenultimate article of the pre-
hensile antenna of the male wholly unarmed, or minutely
and scarcely perceptibly armed.

* The description given herewith is Unit <>f D.fresnanus Lilljeborg, sent by hiin
to de Guerne and Richard, and published by them under the name of I), tyrrelli.

North American Species of Diaptomus. 177

" Outer ramus of the fifth pair of feet in the female Inarticu-
late ; unguiform process of the second segment almost parallel
to the first segment, slightly curved within and minutely ciliate
on the inner margin, the last cilia spine-like. Inner ramus
simple and slender, about equal to the first segment of the
outer ramus ; armed at the outer margin and near the apex
with two medium- sized spines ; apex obtuse and finely hairy.

"Eight fifth foot in the male slender and of medium size.
First segment of the outer ramus with a small hyaline lamella
near the inner apical angle. Second segment comparatively
small and strongly curved ; the outer marginal spine at about
the middle. Terminal hook slightly sigmoid; inner margin
smooth. Inner ramus minute and simple, not reaching the
end of the first segment of the outer ramus.

" Second segment of the outer ramus of the left foot of the
same pair almost triangular ; inner margin slightly sinuate
and ciliate and armed with two obtuse processes (one apical,
the other lateral). Inner ramus indistinctly two-segmented
extending about to the middle of the second segment of the
outer ramus ; minutely hairy within and at the apex.

"Length of female 1.9 mm.; of male 1.8 mm."*

" This Diaptomus is distinguished from all its related forms
by the large lateral lobes of the last thoracic segment. These
lobes, seen from above, are acuminate, but seen from the side,
the posterior extremity is obtuse and armed with two spines.

" The first abdominal segment is remarkable on account of
its long, strong, pointed processes.

" The female of this species slightly resembles 1). ambiguus
Lillj., from Behring Isle, but the lateral projections of the
first abdominal segment are wanting in the latter. ]>. tyrrelli
differs from most other American species in the absence of a
prolongation on the antepenultimate article of the male pre-
hensile antenna.

"The first specimens of this copepod were collected in
Summit Lake, in the Eocky Mountains, at a height of 5,300
feet, and sent to Herr S. A. Poppe by Mr. J. B. Tyrrell, of
Ottawa, Canada.

*Lilljeborg's description from de Ouerne et Richard, "89b.

178 Illinois State Laboratory of Natural History.

"The description given was sent to" us by Prof. Lilljeborg
as that of a new species described by him under the name of
D.fresnanus. It was established from specimens found by
G. Eisen at Centreville, near Fresno, Cal. J>. tyrrelli here
reaches a size somewhat greater than that which it has at
Summit Lake, where it is only 1.5 mm. long."*

Owing to the kindness of Herr Poppe I was enabled to ex-
amine specimens of l>. tyrrelli, but found nothing to add to
the above description. I failed to obtain specimens from Dr.
Lilljeborg, and so am unable to say whether or not there are
minor differences to be found in individuals from the two
localities in which they have hitherto been found.

Diaptomus clavipes n. sp. (PI. XXXIV., Fig. 1-3 ; PL
XXXV., Fig. 1, 2.)

Body of about the same width throughout, except at the
head and at the last thoracic segment, where it narrows
slightly. Last two thoracic segments confluent, the last one
with slightly rounded posterior angles, armed on each side
with a short blunt spine. In the male the body is less
strongly bifid than in the female, and the spines are smaller.
There is but slight difference in the length of the abdominal
segments (PI. XXXV., Fig. 2), the second segment being
longest and about equal to the furcal rami. The first seg-
ment is asymmetrical and armed on each side with a thick
blunt spine, the one on the right side being the more conspic-
uous ; in the male the segment is unarmed. Furcal rami hairy
within ; furcal seta- long, slender, and covered with delicate
hairs.

Antenna? 25-segmented, extending beyond the furcal setae.
Geniculate antenna of the male (PI. XXXIV., Fig. 2) greatly
swollen from the twelfth to the eighteenth segments inclusive.
The armature of the segments is as follows : 1 and 7 have a
sense-club and a long spine ; 2, two long spines, a sense-club,
and a sense-hair; 8, a sense-club and a long seta; 4 and
8, a long spine; 5, a sense-club and a short .-eta: 8, a
short and a long spine; 9, a short spine, a long seta, and a

*De Guerne et Richard, '89b.

North American Species of Diaptomus. 179

sense-club; 10 and 11, two long spines, one much thicker
than the other, and a process; 12, a long spine, a short
spine, and a sense-club; 13, a long spine and a process ; 14,
a long spine, a long seta, and a sense-club; 15, a process,
a long spine, a short seta, and a sense-club; 16, a process, a
long spine, a long seta, and a sense-club ; 17, a plate-like proc-
ess, a long and a short spine ; 18, a plate and a short spine ;
19, 20, and 21 (usually completely ankylosed but some-
times with sutures indistinctly visible), a very long spine, a
long seta, and a short cuticular process ; 22 and 23 (com-
pletely ankylosed), a narrow hyaline lamina (bisected by a
sense hair) and two seta?; 24, two setae; and 25, two long-
seta and two short ones, a sense hair, and a sense-club.

Fifth pair of feet in the male (PL XXXV., Fig. 1) charac-
teristic. First basal segment of the right leg produced at the
inner apical angle into a process (generally blunt but some-
times spine-like) having on the posterior surface a tubercle
bearing a short blunt spine. Second basal segment (PI.
XXXIV., Fig. 1) armed at the inner margin with two proc-
esses, the proximal one broad, prominent, concave toward
the apex of the segment ; the other, slightly above the middle
of the segment, a mere sharp triangular point. At the outer
apical angle is a slight indentation from which springs a del-
icate hair, and from the inner apical angle arises the inner
ramus. First segment of the outer ramus irregular, about
one and a half times as long as broad, with a small sharp tri-
angular-point on the inner margin at about the beginning of
the distal fifth. On this segment is a structure which is not, to
my knowledge, found in any other Diaptomus. This is a hook
arising from the middle of the posterior aspect, and reaching
to the end of the segment. It is sickle-shaped, perfectly
smooth, and although supplied with muscles does not seem to
be movable. Second segment subquadrate, about twice as long
as wide. The marginal spine is short, almost straight, about
a third the length of the segment, delicately serrate within. Ter-
minal hook very stout, as long as the two preceding segments,
tapering gradually, and slightly recurved at the tip ; armed for
the distal two thirds of the inner margin with strong teeth.

180 Illinois State Laboratory of Natural History.

Inner ramus of the right iifth foot short, about the same
breadth throughout, almost reaching the middle of the first
segment of the outer ramus ; armed at the tip with a number
of strong blunt spines.

Second basal segment of the left fifth leg subquadrate, the
inner margin distinctly tuberculate, the outer apical jingle
with a delicate hair. First segment of the outer ramus sub-
quadrate, about a fourth longer than broad ; provided at the
inner margin with a narrow hyaline lamina, produced at the
inner apical angle into a delicately hairy cushion-like process.
The second segment is narrow, about half as broad as the
preceding ; delicately hairy within, and produced at the inner
distal angle into a cushion-like process densely covered with
minute hairs. On the posterior side of this segment are two
processes : one a long straight spine, more than half as long
as the segment itself and armed at the inner margin with
very strong hairs or spinules, largest at the base and decreas-
ing in size toward the tip ; the other a short, thick, blunt
process, perfectly smooth, about a third the length of the
spine.

Inner ramus of left fifth leg very long and narrow, arcuate
(the concavity toward the outer ramus), about one eighth as
broad as long, reaching beyond the end of the first and almost
to the middle of the second segment of the outer ramus. It
is broadest at the base and at the apex, armed at the tip with
a number of strong blunt spinules, and tuberculate its entire
length.

Second basal segment of the fifth pair of feet in the female
(PI. XXXIV., Fig. 3) trapezoidal, with the longest base form-
ing the inner margin. From the outer margin springs the
usual delicate hair. The first segment of the outer ramus is
subquadrate, not quite twice as long as broad. Second seg-
ment subcorneal, almost* straight, a little shorter than the
preceding segment ; the third segment wanting, represented
by two sharp slender spines, the outer more than twice as
long as the inner.

Inner ramus of fifth foot of female, one-segmented, longer
than the first segment of the outer ramus and of uniform

North American Species of Diaptomus. 181

width ; delicately hairy hoth within and without ; apex
bluntly rounded and armed with two spines, the inner long,
sharp, sinuously curved, the outer also sharply pointed hut
oiily ahout half as long as the inner.

Length of female, 1.37 mm. ; of male, 1.28-1.68 mm.

Found (not very abundantly) in material from West Oko-
boji Lake, Iowa, very kindly loaned me by Prof. L. S. Boss,
of Drake University, Des Moines, Iowa.

This species is very similar to Dr. Forbes's D. piscina and
D. leptepus, but the details of structure will serve at once to
distinguish it from them. The hook on the first segment of
the right fifth foot of the male is very characteristic, as are
also the processes on the inner margin of the second basal
segment of the same leg. 1>. clavipes offers such a mass of
peculiar details that it is distinguished with ease from all
other species heretofore described.

The name clavipes was chosen because of the club-like
inner rami of the fifth pair of legs of the male, the inner ramus
of the left leg especially resembling an Indian war- club.

A very curious fact in regard to the distribution of this
species was noted. East and West Okoboji lakes are united
by a very deep, somewhat narrowed channel, but are so nearly
one lake that no account of the division is taken by Rand &
McNally in their atlas. Although there is nothing whatever
to hinder free migration from one part of the lake to the
other, not an individual was found in material from E.
Okoboji, taken the same day and under the same circum-
stances as that from W. Okoboji in which the specimens
were found.

SPECIES INSUFFICIENTLY DESCRIBED.

Diaptomus caroli Heerick.

Diaptomus caroli, Ilerriek and Turner, '95, p. 69.

This species name occurs once in the description of I), sici-
loides (Herrick and Turner '95), but although I have searched
diligently in Herrick's writings for an original description or
even a previous reference to this species, I have been unable

182 Illinois State Laboratory of Natural History.

to find a word in addition to the following. Speaking of D.
siciloides, he says: "This species approaches J>. sicilis
Forbes and I). caroli Herrick very closely, and is said also to
resemble D. gracilis Sars. From caroli it may be at once dis-
tinguished by reason of the fact that the third joint of the
outer ramus of the fifth foot of the female is obsolescent."
The " D. caroli Herrick" would lead one to suppose that it
had been described before ; but, although this work contains
the names and short descriptions of all the other species, 1).
caroli is not among them. I doubt, therefore, whether I am
justified in putting it even under the head of "insufficiently
described" species.

Diaptomus longicornis var. similis Herrick.

Diaptomus longicornis var. similis, Herrick, 1884. p. 141, PL Q, Fig.

5-7.
Diaptomus similis. Herrick and Turner, '95, p. 58.

Something has already been said in regard to this doubtful
species under the head of D. lejptopus. First mentioned in
Herrick's "Final Keport," as one of two varieties, — the other
being the true leptopus as acknowledged by him ('95a), — it
is not mentioned again except in the description of D.francis-
canus, where he says "The form of the fifth feet chiefly sepa-
rates this species from Diaptomus similis Herrick." This
species cannot stand until a more complete description is
written.

DISTRIBUTION OF THE AMERICAN SPECIES OF DIAPTOMUS.

I), sicilis Forbes is one of the most common species in the
Great Lakes, and has been found in Wisconsin, Michigan,
Minnesota, and Yellowstone Park. In Illinois it is recorded
from Cedar Lake and Fox Lake.

D. piscinae Forbes has been recorded only from Yellowstone
Park, and I now add Portage Slough, Manitoba, Can.

D. lintoni Forbes has been found only in Yellowstone
Park.

I), leptopus Forbes is found in Massachusetts, Wisconsin,
Minnesota, and Illinois.

North American Species of Diaptomus. 183

D. sanguineus Forbes is very common throughout central
and southern Illinois, and has been recorded from New York,
Wisconsin, -Minnesota, and Alabama.

1>. stagnalis Forbes is also a common species, and is re-
corded from Minnesota, Illinois, Ohio, Kentucky, and Ala-
bama.

I), shoshone Forbes has never been found outside of Yellow-
stone Park.

D. pallidus Herrick is an exceedingly common species in
central Illinois and has been recorded from Ohio, Wisconsin,
and Minnesota.

1>. albuquerquensis Herrick was first described from Albu-
querque, N. M., and is also found in Florida.

I), novamexicanus Herrick has only been recorded from
Albuquerque, N. M.

I), oregonensis Lilljeborg is a very common species in Illi-
nois, occurring generally with 1>. siciloides Lillj. and 1). palli-
dus Herrick. It is also common in Wisconsin and is found
in Michigan, Minnesota, and Oregon.

I). siciloides Lilljeborg is found in immense numbers at
Havana, 111. I have found it also in Iowa and Indiana col-
lections, and it was originally described from L. Tulare,
Fresno, Cal.

1>. mi tint its Lilljeborg is probably the common species in
the northern tier of states. It has been found in Yellowstone
Park, in the Great Lakes, and in Wisconsin, Michigan,
Newfoundland, Greenland, and Iceland.

D. franciscanus Lilljeborg has been found only by G.
Eisen, near San Francisco, Cal.

/>. elseni Lilljeborg is also a California species.

1). signicauda Lillj., one of the most peculiar of American
species, is recorded only from the Sierra Nevadas.

J>. trybomi Lilljeborg is recorded only from Multnomah
Falls, Oregon.

7). ashlandi Marsh seems to be the most widely distributed
of American forms, having been found in the Great Lakes,
in Indiana, Michigan, Wisconsin, Oregon, Idaho, Washing-
ton, and in Yellowstone Park.

184 Illinois State Laboratory of Natural History.

D. reighardi Marsh has been recorded only from New
Lisbon, Wisconsin.

D. mississippiensis Marsh is common in Mississippi, and
has been found in Florida in connection withD. albuquerquen-
sis Herrick.

D. tyrrelli Poppewas described by the author of the species
from Summit Lake, and by Lilljeborg, under the name D.
fresnanus, from Fresno, near Centreville, Cal.

I), clavipes n. sp. is described in this paper from West
Okoboji Lake, Iowa.

North American Species of Diaptomus. 185

GENEKAL BIBLIOGRAPHY* OF THE GENERA DIAP-
TOMUS, EPISCHURA, LIMNOCALANUS,
AND OSPHRANTICUM.

This bibliographical list has been prepared principally in further-
ance of Dr. SehmeiTs purpose to compile a complete bibliography of
the Copepoda of the world. To this end the list published by him in
his Monograph (Schmeil, '96) has been critically reviewed and in some
instances corrected, and a number of additions have been made. New
species described since the publication of de Guerne and Richard's
Revision ('89b) are noted in connection with the articles containing the
original descriptions.

All articles except those marked with an asterisk are in the library
of the Illinois State Laboratory of Natural History or in that of the
University of Illinois.

Apstein, C.
'92. (See Article II.)

'96. Das Siisswasserplankton. Methode und Resultate der quantita-
tiven Untersuchung. 201 pp.. 113 Abbild., 5 Tab. Kiel u. Leipzig.
Review, Zool. Centralbl., III. Jahrg., No. 22, pp. 764-769.

Aurivillius, C. W. S., u. Cleve, P T.
'96. DaS Plankton des Baltischen Meeres. Bihang till K. Svenska
Vet.-Akad. Handl.. Bd. XXL, Afd. IV., No. 8, pp. 1-83, Taf. L, II.;
Abstract, Zool. Centralbl., IV. Jahrg., 1897, No. 16, pp. 546-550.

Baird, W.
'50. (See Article II.)

Barrois, Th.
'91. Sur trois Diaptomus nouveaux des environs du Caire. Rev.

Biol, du Nord de la France, T. III., Nos. 6, 7, 8.
*'95. Contribution a l'etude de quelques lacs de Syrie. Rev. Biol.

du Nord de la France, T. VI., No. 6, pp. 224-240; Abstract, Biol.

Centralbl., XV. Bd., Nr. 24, pp. 869-S73.
*'96. Recherches sur la faune des eaux douces des Agores. Mem.

Soc. sci., agr., arts, Lille, Ser. V., Fasc. VI. 172 pp., 3 cartes; Abstract,

Zool. Centralbl., III. Jahrg., No. 18, pp. 609-611.

Birge, E. A.
'95. On the Vertical Distribution of the Pelagic Crustacea of Lake
Mendota, Wis., during July, 1894. Biol. Centralbl., XV. Bd., Nr. 9,
pp. 353-355.

*As the bibliographical list published in connection with the preceding paper,
Article II. of this series, contains a large number of titles identical with those of this
bibliography, these duplicate titles are not reprinted here, but reference is made,
under the author's name and the year of publication, to the bibliographical list of the
preceding article.— S. A. Forbes.

186 Illinois State Laboratory of Natural History.

'95a. Plankton Studies on Lake Mendota. I. The Vertical Distri-
bution of the Pelagic Crustacea during July, 1894. Trans. Wis.
Acad. Sci.. Arts, and Letters, Vol. X., pp. 421-184, Pis. VII.-X.

'95b. Turkey Lake as a Unit of Environment, and the Variation of
its Inhabitants: Cladocera.f Proc. Ind. Acad. Sci., 1895, No. 5.
p. 245.

'97. The Vertical Distribution of the Limnetic Crustacea of Lake
Mendota. Biol. Centralbl., XVII. Bd., Xr. 10, pp. 371-375.

Blanchard, R.
'90. Sur une matiere colorante des Diaptomus. analogue a la carotine
des vegetaux. Compt. Rend, de l'Acad. des Sci., Paris, T. CX., pp.
292-294.

'90a. Sur une carotine d'origine animale, constituant le pigment
rouge des Diaptomus. Mem. de la Soc. zool. de France, T. III.,
p. 113.

Blanchard, R., et Richard, J.
'90. (See Article II.)
'91. (See Article II.)

'97. Sur la faune des lacs feleves des Hautes-Alpes. Mem. de la Soc.
zool. de France, T. X., pp. 43-61.

Brady, G. S.
'68. (See Article II.)
'78'80. (See Article II.)

'86. Xotes on Fresh-water Entomostraca from South Australia.
Proc. Zool. Soc. London, 1886, pp. S2-84. 3 Pis.

'86a. Xotes on Entomostraca collected by Mr. A. Haley in Ceylon
Journ. Linn Soc. London, Zool., Vol. XIX., pp. 293-317, PI.
XXXVIL, Fig. 21-26.

'91. (See Article II.)

Buchholz, R.
*'74. Crustaceen. Die zweite deutsche Xordpolfahrt in den Jahren
1869 u. 1870, Bd. II., pp. 262-398. 15 Pis.

Bundy, F. W.
'82. A List of the Crustacea of Wisconsin. With Xotes on some
*Sew or Little-known Species. Trans. Wis. Acad. Sci., Arts, and
Letters, 1877-S1, Vol. V., pp. 176-184.

Cajander, A. H.
'69. Bidrag till kannedom om sydvestra Finlands Krustaceer. Xot.
Sallsk. pro Fauna et Flora Fennica Forh., Heft X., pp. 373-376.

tKeference to Diaptomus and to Epischura lacustris.

North American Species of DiaptOmus. 187

Chambers, V. T.
'81. Two New Species of Entomostraea. Journ. Cincinnati Soc. Nat.
Hist., Vol. IV., pp. 47, 48. 2 Pis.

Chyzer, C.
'58. Uber die Crustaeeenfauna Ungarns. Verb., d. K.-K. zool.-bot.
Gesellsh. Wieu, Bel. VIII., p. 505.

Claus, C.
'58. (See Article II.)
'63. (See Article II.)
'76. (See Article II.)

*'77. Die Schalendriise der Copepoden. Sitzungsber. Akad. Wien,
Math. Nat. CI., LXXIV. Bd.. I. Abtb., pp. 717-721. 1 PI.

'88. Uber den Organistnus der Nebaliden und die systeinatische
Stellung der Leptostraken.f Arb. zool. Inst. Univ. Wien, VIII. Bd.,
pp. 1-148. Taf. I.-NV.

'93. (See Article II.)

'93a. (See Article II., '93b.)

'93b. (See Article II., '93c.)

'95. Uber die Wiederbelebung im Schlammeeingetrockneter Copep-
oden und Copepoden-Eier. Zugleich ein Beitrag zur Kenntniss von
Microcyclnps diaphanus (Fiscb.) = minutus (Cls.). Arb. Zool. Inst.
Univ. Wien, T. XI., 1 Heft, pp. 1-11, Taf. I., II.

'95a. Uber die Maxillarfiisse der Copepoden und die morphologi-
sche Deutung der Cirripedien-Gliedmassen. Arb. Zool. Inst. Univ.
Wien, T. XI., 1 Heft, pp. 49-63, Taf. VIII.

Cragin, F. W.
'83. (See Article II.)

Daday, E. v.

'84. Catalogus Crnstaceorum faunae Transylvania?, (e collectione
Musei transylvanici, collegitet determinavit). [Latin title of Hun-
garian article.] Orv. Termeszettud. Ertesito, Vol. IX., pp. 1G1-187

'85. (See Article II., 85a.)

'85a. Ujallatfajok Budapest edesvizi faunajabol. Term, fiiz., Vol.
IX., p. 127, PI. XI.

'85b. (See Article II., '85.)

*'90. Conspectus Diaptomorum fauna 1 hungariere. Math, naturw.

Berichte a. Ungarn, Bd. XIII., pp. 114-143, Pis. IV.-V1.
*'90a. Ubersicht der Diaptoraus-Arten Ungarns. Math, naturw.

Berichte a. Ungarn, Bd. XIV., pp. 177-1SO.

tFutterung mit Farbstoffen an Diaptomus, pp. 99, 101.

188 Illinois State Laboratory of Natwral History.

'91. Adatok Magyarorszag edesvizi mikroskopos faunajanak isme-
retehez. Term fiiz., Vol. XIV., pp. 16-31, PI. I. Also in German:
Beitriige zur Mikr.opisehen Siisswasserfauna Ungarns, Ibid., pp. 107-
123.

'91a. Az eddig pontosan ismert Diaptomus-fajok meghatarozo tab-
lazata. Tabella synoptica specierum generis Diaptomus hucusque
recte cognitarum. [Article in Hungarian and Latin.] Term, fiiz.,
Vol. XIV, pp. 32-51.

'97. Beitriige zur Kenntniss der Miorofauna der Tatra-Seen. Term,
fiiz., Vol. XX., pp. 149-196.

Dahl, Fr.
*'94. Die Copepodenfauna des unteren Amazonas. Ber. d. naturf.
Gesellseh. zu Freiburg, i. B., Bd. VIII., pp. 10-23, Taf. I., Fig. 1-4.
Diaptomus kensenii n. sp.
'95. Neueres iiber Morphologie unci Ethologie der Copepoden. Zool.
Centralbl., II. Jahrg., No. 22 u. 23, pp. 673-678.

De Kay, J. E.

'44. Crustacea. Xat. Hist. New York, Zoology, Part VI., pp. 1-65.
Pis. I.-XIII.

Eusebio, J. B.
'88. Becbercbes sur la faune des eaux du Plateau Central. La Faune
pelagique des lacs d'Auvergne. Kev. d'Auvergne (Clermont-Fer-
rand) [Fide Scbmeil]. Separate, pp. 1-29, PI. I., Fig. 10.

Fellows, C. S.
'87. A description of Ergasilus cJiautauquaensis, a New Species of
Copepoda, and a List of other Entomostraca found at Lake Chau-
tauqua in August, 1886. Proc. Am. Soc. Microscopists, 1887. 4 pp.,
1 PI.

Ferussac, D. de
*'06. Memoire sur deux nouvelles especes d'Entomostraces et d'Hy-
drachnes (Cyclops miilleri[_= Diaptomus ccsruleus] and Cypris renifor-
mis). Ann. Mus. hist, nat., T. VII., p. 213.

Fischer, S.
*'51. Beitriige zur Kenntniss der in der Umgegeud von St. Peters-
burg sich fiudenden Cyclopiden. Bull. Soc. Imp. des Naturalistes
de Moscou, T. XXIV., Pt. II., pp. 409-438, Pis. IX., X.

*'53. Beitriige zur Kenntniss der in der Umgegend von St. Petersburg
sich findenden Cyclopiden. Fortzetzung. Bull. Soc. Imp. des Xat-
uralistes de Moscou, T. XXVI., Pt. II., No. 1, pp. 74-100, Pis.
II., III.

Forbes, S. A.
'76. (See Article II.)

Noiilt American Species of Diaptomus. 189

'78. The Food of Illinois Fishes. Bull. 111. State Lab. Xat. Hist,
Vol. I., No. 1, pp. 71-89.

'78a. On the Crustacea eaten by Fishes. Bull. 111. State Lab. Nat.

Hist, Vol. I., Xo. 2, p. 87.
'80. The Food of Fishes. Bull. 111. State Lab. Nat. Hist., Vol, I.,

No. 3. pp. 18-65; Rep. 111. State Fish Comm., 18S4. pp. 90-127.

'80a. On the Food of Young Fishes. Bull. 111. State Lab. Nat. Hist.,
Vol. I., No. 3, pp. 60-79.

'82. On the First Food of the Young White Fish. American Field,
Mar. 11,1882.

'82a. (See Article II.)

'82b. (See Article II., '82.)

'83. The Food of the Smaller Fresh-water Fishes. Bull. 111. State Lab.
Nat. Hist., Vol. I., No. 6, pp. G5-95; Rep. Bd. 111. State Fish. Comm.,
1886, pp. 114-138.

'83a. The First Food of the Common AVhite-Fish {Coregonus clupei-
formis Mitch.). Bull. 111. State Lab. Nat. Hist,, Vol. I., No. 6, pp.
95-109; Rep. Bd. 111. State Fish Comm., 1886, pp. 139-149.

'87. (See Article II.)

'90. (See Article II. '90a.)

'90a. (See Article II. '90.)

'93. (See Article II.)

Forel, A. F.
'78. Faunistische Studien in den Siisswasserseen der Schweiz. Zeit-
schr. f. wiss. Zool., Bd. XXX., Suppl., pp. 383-391.

'82. Die pelagische Fauna der Siisswasserseen. Biol. Centralbl., II.
Bd., Nr. 10, pp. 299-305: Translation, Ann. Mag. Nat. Hist., Vol. X.,
p. 320.

France, R. H.
'94. Zur Biologie des Planktons. Vorliiufige Mitteilung. Biol. Cen-
tralbl., XIV. Bd., Nr. 2, pp. 33-38.

Fric (Fritsch), A.
'72. (See Article II.)

'95. Uber Parasiten bei Crustaceen und Riiderthieren der siissen Ge-
wiisser. Bull. Internat'n'l d"Acad. des Sci.de TEmpereur Frangois
Joseph I , Classe des Sci. Math, et Nat., pp. 1-7.

'95a. (See Article II. "95.)

Fritsch. (Fric ), A., u. Vavra, V.
'92. (See Article II.)
'94. (See Article II.)

190 Illinois State Laboratory of Natural History.

Fric, J. A.
'82. (See Article II.)

Gadeau de Kerville, H.
'88. Les Crustaces de la Normandie: espeees fluviales, stagnates efc
terrestres; premiere liste. Bull, de la Soc. des Amis des Sci. nat. de
Rouen, 1888, l re Sem., pp. 133-158.

Garbini, A.
'93. Prirai Materiali per una Monografia Limnologica del Lago di

Garda. III. Limnofauna. Estr. dal Vol. LXIX., Ser. III., dell'

Aeead. Agric, Arti, e Comm. di Verona, pp. 28, 37, 49.
'94. (See Article II.)
'95. Fauna Limnetica e Profonda del Benaeo. Boll. Mus. di Zool.

ed Anat. eomp. della Univ. di Torino, Vol. X., Xo. 198, pp. 2, 4, 5.
'95a. Appunti di Careinologia Veronese. I. Elenco dei Crostacei

veronesi. Estr. dal Vol. LXXI., Ser. III., Fasc. I., dell'Accad. di

Verona, p. 3.
'95b. Appunti di Careinologia Veronese. II. Considerazione ecolog-

iche e corologiehe. Estr. dal Vol. LXXI., Ser. III., Fasc. 1, dell'

Accad. di Verona, pp. 9, 14.
'95c. Distribuzione e Intensita della Fauna atesina. Estr. dal Vol.

LXXI., Ser. III., Fasc. II., dell' Acead. di Verona, p. 10.

Gerst acker, A.

'54. Bericht iiber die Leistungen in der Xaturgeschichte der Crusta-
ceen, Araehniden, und Myriapoden wiihrend des Jahres 1852 und
1853. Arch. f. Xaturgesch., XX. Jahrg., Bd. 2, pp. 72-108.

'63. Copepoda. Handbuch der Zoologie, pp. 402, 403. Leipzig.

'66-'79. Copepoda. Bronn's Klassen und Ordnungen des Thier-
reichs, V. Bd., I. Abtheil., pp. 590-806.

Giesbrecht, W.

'81. Vorlauflge Mitteilung aus einer Arbeit iiber die freilebenden
Copepoden des Kieler Hafens. Zool. Anz., XIV. Jahrg., No. 83, pp.
254-258.

'82. Die freilebenden Copepoden der Kieler Fohrde. IV. Ber. d.
Xotnm. z. w. Unters. d. deutsch. Meerein Kiel, pp. S7-168, Taf. I-X 1 1 .

'92. Sj'stematik und Faunistik der pelagisehen Copepoden des Golfs
von Xeapel und der angrenzenden Meeres-abschnitte. XIX. Mono-
graph, der Fauna und Flora des Golfs von Xeapel. S31 pp., 54 Pis.
Berlin.

'93. Mitteihingen iiber Copepoden. G. Zur Morphologie der Maxil-
lipeden. Mitteilungen a. d. zool. Stat, zu Xeapel, Bd. XL, Heft
I., pp. 83-102.

North American Species of Diaptomus. 191

'95. Mitteilungen iiber Copepoden. 7. Zur Morphologie des weib-
lichen Abdomens. Mitteilungen a. d. zool. Stat, zu Xeapel, Bd.
XL, Heft IV., pp. 031-648.

Gissler, C. F.

'81. Variations in a Copepod Crustacean. Am. Nat., Vol. XV., pp.

6S9-698.

'81a. Note regarding Change of Color in Diaptomus sanguinexis.
Am. Nat., Vol. XV., p. 7-12.

Grobben, C.
'80. Die Antennendriise der Crustaceen. Arb. Zool. Inst. Univ.
Wien, Bd. III., pp. 93-110, Taf. IX.

'92. Zur Kenntniss des Stammbaumes und des Systems der Crusta-
ceen. Sitzungsber. der K. Akad. der Wissensch. in Wien, Math-
naturw. Classe, Bd. CI., Abt. I., Jan., 1892, pp. 1-38.

Gruber, Aug.
'78. fiber Bildung und Wirkung der Spermatopboren bei Diaptomus
gracilis und Heterocope robusta. Dissertation. Promotionsschrift
zur Erlangung der Doktorwiirde. der philosoph. Facult. der Univ.
Leipzig vorgelegt. 34 pp., 2 Pis. Leipzig.

'78a. Die Bildung der Eiersackchen bei den Copepoden. Zool. Anz.,
I. Jahrg., No. 11, p. 247.

Guerne, J. de
'86. Description du Centropages grimaldii, Copepode nouveau du
golfe de Finlande. Bull, de la Soc. zool. de France, T. XL, pp.

276-2S5.

'87. Sur les genres Ectinosoma Boeck et Podon Lilljeborg. a propos
de deux Entomostraces (Ectinosoma atlanticum G. S. Brady et Kob-
ertson, et Podon minutus G. O. Sars) trouves a la Corogne dans
Testomac des sardines.f Bull.de la Soc. zool. de France, T. XII.,
p. 29.

Guerne, Jul. de, et Richard, J.
'88. Sur la distribution geographique du genre Diaptomus. Compt.

rend, de l'Acad. des Sci., 2 juillet, 1888. 3 pp.
'88a. Diagnoses de deux Diaptomus nouveaux d'Algerie (D. blan-

cJiardi et D. lilljehorgi). Bull, de la Soc.zool.de France, T. XIII. ,

pp. 160-162.

'89. (See Article II., '89a.)
'89a. (See Article II., '89.)

'89b. Eevision des Calanides d'eau douce. Mem. de la Soc. zool. de
France. T. II., pp. 53-181, Pis. I.-IV. and 60 fig. in text.

tReference to Limnocalanus grimaldii.

192 Illinois State Laboratory of Natural History.

'90. La distribution geographique des Calanides d'eau douce. Asso-
ciation franeaise pour 1' a van cement des sciences fusionee avec
1' Assoc, scient. de France, Congres de Paris. Seance du 14 aoiit.1889.
5 pp., 1 PL

'90a. Diagnose d'un Diaptomus nouveau du Congo (2>. loveni). Bull,
de la Soc. zool. de France, T. XV., pp. 177. 178.

'90b. Description du Diaptomus alluaudi n. sp., recueilli par M.
Alluaud dans un reservoir d'eau douce a Lanzarotte (Canaries).
Bull, de la Soc. zool. de France, T. XV., pp. 198-200.

'90c. On the Fresh-Water Fauna of Iceland. Ann. and Mag. Xat.
Hist., Series VI.. Vol. X., pp. 340-342.

'91. (See Article II.)

'91a. Synonymie et distribution geographique de Diaptomus alluaudi.
Bull, de la Soc. zool. de France, T. XVI., pp. 213-217.

'91b. (See Article II., '91a.)

'91c. Entoinostraefes recueillis par M. Charles Raboten Russie et en
Siberie (Gouvernements de Kasau, de Perm, de Vologda, et de
Tobolsk). Bull, de la Soc. zool. de France, T. XVI., pp. 232-236.

'92. Sur.la faune des eaux donees de l'Islande. Compt. rend, de
PAcad. des Sci., T. CXIV., pp. 310-313.

'92a. (See Article II.)

'92b. Documents nouveaux sur la distribution geographique des
Calanides d"eau douce. Assoc, franc, pour l'avanc. des Sci.. Con-
gres de Marseille, 1S91, T. XX.. Plate V. 5 pp. Paris.

'92c. (See Article II., '92b.)

'93. (See Article II.)

*'94. Diaptomus chevreuxi, Copepode nouveau d'Algerie. Bull, de la

Soc. zool de France, T. XIX., p. 176.
'96. Premiere liste des Copepodes et Cladoeeres d'eau douce du

Portugal. Bull, de la Soc. zool. de France, T. XXI., pp. 157-159.
'96a. D. bland, Copepode nouveau recueilli par M. Edouard Blanc a

Boukhara (Turkestan). Bull, de la Soc. zool. de France. T. XXL.

pp. 53-56. 5 Fig.

Hacker, F.
*'95. Die Vorstadien der Eireifung. Zusammenfassende Unter-
suchungen tiber die Bildung der Vierergruppen und das Verhalten
der kernbliischennucleolen. Arch. f. mikr. Anat., Bd. 45, pp. 200-
273; Abstract, Zool. CentralbL, 11. Jahrg.. Xr. 18, pp. 551-553.

Hansen, H. J.
'93. Zur Morphologic der Cliedmassen und Mundteile bei ( 'rustaeeen
und Insekten. Zool. Anz., XVI. Jahrg., Nos. 420 u. 421, pp. 193-19S,
201-212.

North American Species of Diaptomus. 193

Hartog, M. M.
'80. On the Anal Respiration of the Copepoda. Quart. Journ. Micros.

Sci. London, Vol. XX., pp. 24-1-245: Proc. Manchester Lit. and

Philos. Soc, Vol. XIX., pp. 61, G2.
1 82. Del' oeil impair des Crustaces. Compt. rend. Acad. Paris, T.

XC1V., pp. 1430-1432; Ann. Mag. Nat. Hist,, Vol. X., pp. 71,72;

Archiv Zool. Experim., Vol. X., pp. 7, 8.
'88. (See Article II.)

Hartwig, W.
'93. (See Article II.)
'94. (See Article II.)

'97. Znr Verbreitung der uiederen Crustaceen der Provinz Bran-
denburg. Forschungsber. a. d. Biol. Stat, zu Plon, Theil V., pp.
115-149. Stuttgart.

Heller, C.

'71. (See Article II.)

Herrick, C. L.
'77. A Xew Cyclops.f Geol. and Xat. Hist, Surv. of Minn. 5th Ann.
Rep., pp. 238-239. 2 Figs.

'79. (See Article II.)

'79a. Fresh-water Entomostraca. Am. Xat.. Vol. XIII., pp. 620-629.
4 Pis.

'82. (See Article IL,'82a.)
'83. (See Article II.)
'83a. (See Article II.)
'84. (See Article II.)
'87. (See Article II.)

'95. Micro-Crustacea from Xew Mexico. Zool. Anz., XVIII. Jahrg.,
Nr. 467, pp. 40-47. 2 Taf.

D. albuquerquensis and D. novamezicanus.

Herrick, C. L., and Turner, C. H.
'95. (See Article II.)

Hoek, P. P. C.

'76. (See Article II.)

*'77-'78. Zur Entwickelungsoeschichte der Entomostraken. II. Zur
Embryologie der freilebenden Copepoden. Xiederl. Arch. f. Zool.
Bd. IV.. pp. 55-74. Taf. V.-VI.

'78. (See Article 11.)

Imhof, O. E.
'83. (See Article II.)

fDiaptouius sp. V

194 Illinois State Laboratory of Natural History.

'84. Resultate meiner Studien iiber die pelagische Fauna kleiner
und grosserer Siisswasserbecken in der Schweiz. Zeitschr.f. wiss.
Zool., Band XL., pp. 154-178.

'84a. (See Article II., '84.)
'85. (See Article II., '85a.)
'85a. Uber die blassen Kolben an den vorderen Antennen der Siiss-

wasser-Calaniden. Zool. Anz., VIII. Jabrg., Nr. 107, p. 353.
'85b. (See Article II., '85.)
'86. (See Article II.)
'86a. (See Article II., '86b.)
'87. Uber die microseopiscbe Tbierwelt bocbalpiner Seen (000-

2780 in. u. M.). Zool. Anz., X. Jahrg., Nos. 241 u. 242. pp. 13-17,

33-42 ; Abstract, Am. Nat., Vol. XXI.. p. 071.

'87a. (See Article 11.)
'87b. (See Article II.)

'88. Fauna der Siisswasserbecken. Zool. Anz., XI. Jahrg., Nos. 275
u. 270, pp. 106-172, 185-190.

'88a. (See Article II., '88.)

'90. (See Article II., '90a.)

'90a. (See Article II.. '90.)

'90b. Notizen iiber die Siisswasser-Calaniden. Zool. Anz., XIII.
Jahrg., Nos. 349 u. 350. pp. 029-033, 054-658.

'91. Uber die pelagische Fauna einiger Seen des Schwarzwaldes.
Zool. Anz , XIV. Jahrg., No. 355, pp. 33-38.

'92. Zusammensetzung der pelagischen Fauna der Siisswasserbecken.
Biol. Centralbl., XII. Band., Nr. 6, 7 u. 8, pp. 171-182, 200-205.

*'93. Les organismes inf erieurs des lacs a la region du RhOne. Arch.
des Sci. phys. et nat., octobre — decembre, 1893.

'94. Fauna hochgelegener Seen. Seen der Rocky-Mountains, Nord-
Amerika. Von S. A. Forbes. Biol. Centralbl., XIV. Bd., Nr. 8,
pp. 287-293.

'95. (See Article II.)

'96. Die Binnengewiisser Fauna der Azoren ; Referat nach de Guerne
und Barrois. Biol. < VntralbL. XVI. Bd., Nr. 18, pp. 683-688.

Jurine, L.
'20. (See Article II.)

Kafka, Josef.
'92. (See Article II.)

Kerville, H. (See Gadeau de Kerville, H.)

North American Species of Diaptomus. 195

King, It. L.

*'55. On Australian Entomostracans. Papers and Proc. Roy. Soc.
Van Dieinen's Land, Vol. III., Pt. I.

Koch, C. L.
'35-'41. Deutschlands Crustaeeen, Myriapoden, und Arachniden,
Heft. XXL, XXXV. Kegensburg.

Koelbel, C.
'85. ("arcinologisches. Sitzungsber. d. K. Akad. d. Wiss. Wien,
Math, naturw. Klasse., Bd. XC. 1 Abteil., pp. 312-323, PI. I , Fig.
1-5.

Kortchaguine, A. N.
*'87. Fauna der Umgebung Moskaus. I. Crustaeeen [German title
of Russian article]. (Arb. aus. d. Laborat. d. Zool. Mus. der Univ.
Moskau.) Sehriften der Gesellsch. v. Freundeu d. Xaturwis-
sensch. zu Moskau, Bd. LIT.

Ladenburger, It.
'84. Zur Fauna des Mansfelder Sees. Zool. Anz., VII. Jahrg., Nr.
1GS, pp. 299-302.

Lauterborn, It.
'94. Uber die Winterfauna einiger Gewiisser der Oberrheinebene.
Mit Beschreibungen neuer Protozoen. Biol. Centralbl., XIV. Bd.,
Xr. 11, pp. 391-398.

'94a. Beitriige zur Stisswasserfauna der Insel Helgoland. TYissen-
sehaftliehe Meeresuntersuchungen, "Xeue Folge,'' Bd. I., Heft 1. pp.
216-221.

Leydig, Fr.

'59. Bemerkungen iiber tlen Bau der Cyclopiden. Arch. f. Xaturg.
XXV. Jabrg., I. Bd., pp. 194-207, Taf. IV.

Lilljeborg, "W.
'53. (See Article II.)
'63. Beskrifning ofver twa arter Crustaceer af ordingarne Ostracoda

och Copepoda. Ofv. af K. Vet.-Akad. Forbandl., Arg. XIX.. p. 391.
'87. On the Entomostraca collected by Mr. Leonhard Stejneger, on

Bering Island. 1882-83. Contributions to the Natural History of

the Commander Islands. Proc. U. S. Xat'n'l Mus., 18S7, pp. 154-15(5.
'88. Descriptions de deux especes nouvelles de Diaptonius du nord de

l'Europe. Bull, de la Soc. zool. de France, T. XIII., pp. 156-158.

Lubbock, J.
*'53. On two New Species of Calanidre, with Observations on the
Spermatic Tubes of Pontella, Diaptomus, etc. Ann. Mag. Nat. Hist.,
Vol. XII., pp. 1 15-124, 159-165, Pis. V., VI.

196 Illinois State Laboratory of Natural History.

*'54. On the Fresh-water Entomostraca of South America. Trans.
Entoru. Soc. X.S., T. III.

*'56. On some Entomostraca collected by Dr. Sutherland in the At-
lantic Ocean. Trans. Entom. Soc. London, Vol. IV., Part II., pp.
8-39, Pis. II.-XI1.

*'57. Description of eight New Species of Entomostraca found at
Weymouth. Ann. Mag. Nat. Hist., Vol. X X., pp. 101-410. Pis. X.. XI.

*'60. On Some Oceanic Entomostraca collected by Capt. Toynbee.

Trans. Linn. Soc. London, Vol. XXIIL, pp. 295, 296; Ann. Mag.

Nat. Hist., Vol. XL, pp. 48S, 489.
'63. (See Article II.)

Maitland, It. T.
*'74. Naamlijst van Nederlandsche Schaldieren. Tijdschr. Nederl.
Dierk. Vereen., 1 Deel, pp. 228-269.

Marenzeller, E. v
'73. Uber Diaplomus amblyodon n. sp. Verb. d. K. K. zool.-bot. Ge-
sellsch. Wien, Bd. XXIIL, p. 593, Taf. VI.

Marsh, C. D.
'91. (See Article II.)

'92. (See Article II.)
'93. (See Article II.)
'93a. (See Article II.)

'94. On two New Species of Diaptomus. Trans. Wis. Acad. Sci.,
Arts, and Letters, Vol. X., pp. 15-17, PI. I.
D. mississipi>iensis and D. I>ir<j< j i, n. sp.

'95. (See Article II.)

'97. On the Limnetic Crustacea of Green Lake. Trans. Wis. Acad.
Sci.. Arts, and Letters, Vol. XL, pp. 179-224, Pis. V.-XIV.

Milne-Edwards, H.
'34-'40. (See Article II.)

'38. Extrait d' un Mcmoire sur la distribution geographique des
Crustaces. Compt. rend, des Seanees de l'Acad. des Sci. 9 pp.

Moniez, It.

'87. (See Article II.)
'89. (See Article II., '89a.)

Mrazek, A.

'91. (See Article II.)

'93. Pfi'spevky k poznani sladkovodnich Copepodu [Contributions
to the Knowledge of Fresh-water Copepoda ]. Vestnik Krai. Ceskfi
Spol. Nauk. Tfida math.-prir., 1893. 74 pp., 8 Pis.; Abstract, Zool.
Centralbh, 1. Jahrg., pp. 593, 594.

North American Species of Diaptomus. 197

'93. (See Article II., '93c.)

'95. (See Article II.)

*'96. Zwr Entwickelungsgesehiehte einiger Taenien.t Sitzungsber.

el. k. bohm. Gesellscb. Wiss. Math.-nat. Classe. 16 pp., 1 PI.;

Abstract. Zo'ol. Centralbl., IV. Jabrg., No. 15, pp. 522, 523.

M idler, 0. F.

1792. (See Article II.)

Nice-let.
*'48-'49. Crustaceos. In Gay, C, Historia fisica y politiea de Chile
etc., Zoologia, Vol. III., pp. 288-292.

Nordqvist, O.
'86. (See Article II.)
'87. (See Article II.)
'88. Die Calaniden Finlands. Bidrag till Kannedom af Finlands

Natur och Folk. Utgifva af Finsva Vetensk.-Soc, Heft 47, pp.

192-275. 10. Pis.
'89. liber einen Fall von androgyner Missbildung bei Diaptomus

gracilis G. O. Sars. Arch, f . Naturgesch. Jabrg. LV., pp. 241-243,

Taf. XI I.
'90. (See Article II.)

Norman, A. M.
'86. Museum Normanianum ; or a Catalog of the Invertebrata of
Europe and the Arctic and North Atlantic Oceans, pp. 22, 23.

OuchakofF, N.
*'55. Pontie de Wacarino. Bull, de la Soc. imp. des natural, de Mos-
cou, T. XXVIII.

Pavesi, P.
'79. (See Article II.)
'79a. (See Article II.)
'83. (See Article II.)

Pickering, C.
'44. Generic Description of Scopiphora vagans. Nat. Hist. N. Y.,
Zool., Part VI., Crustacea, p. 62.

Pitard, E.
*'97. Sur le Plankton du lac de Joux. Arch. Sci. phys. et nat., A' ms

per.. T. III. 3 pp.
*'97a. Sur le Plankton du lac Brenet. Arch. Sci. phys. et nat., 4' :ae
per.,T. III. 2 pp.

Poggenpol, M. J.

'74. (See Article II.)

tContains reference to Diaptomus.

198 Illinois State Laboratory of Natural History.

Poppe, S. A.
'84. Bemerkungen zu R. Ladenburger's: Zur "Fauna ties Mans-

felder Sees" in No. 108 des Zoologischen Anzeigers. Zool. Anz.,

VII. Jahrg., No. 176, pp. 499, 500.
'86. Ein neuer Diaptomvs aus dem Hirschberger Thai. Zeitschr. f.

wiss. Zool., Bd. 43, pp. 285-289, Taf. X., Fig. 1-12.

'88. Diagnoses de deux especes du genre Diaptomus Westwood.
Bull, de la Soe. zool. de France, T. XIII., pp. 159, 1G0.

'89. (See Article II.)
'89a. (See Article II.)

'91. Ein neuer Diaptomus aus Brasilien. Zool. Anz., XIV. Jahrg.,
No. 308, pp. 248-250. 3 Fig.
[D. deitersi n. sp.]

Poppe, S. A., u. Mrazek, A.
'95. Entouiostraken des Naturhistorischen Museums in Hamburg.

1. Die von Herrn Dr. F. Stuhlmann auf Zanzibar und dem gegenliber-
liegenden Fesilande gesammelten Siisswasser-Copepoden. 2. Taf.

2. Entomostraken von Sud-Georgien. 1 Taf. 3. Die von Herrn
Dr. H. Driesch auf Ceylon gesammelten Susswasser-Entomostra-
ken. I Taf. Beiheft zum Jabrb. der Hamburgischen wissenscbaftl.
Anstalten. XII. 20 pp.

Poppe, S. A., et Richard, J.
'90. (See Article II.)

'92. Description du Diaptomus schmackeri n. sp., recueilli par M.
Schmacker dans le lac Tahoo (Chine). Bull de la Soc. zool. de
France, T. XVII., pp. 149-151. 6 Fig.

Rath, O. v.
'91. (See Article II.)

Rehberg, H.
'80. (See Article II., '80a.)
'80a. (See Article II., '80b.)

Richard, J.
'87. (See Article II.)

'87a. Sur la faune pelagique de quelques lacs d'Auvergne. Conipt.

rend. d'Acad. des Sci., 14 novembre et 12 decembre, T. CV. pp.

951-953.
'88. Entomostraces nouveaux on pen connus. Bull, de la Soc. zool.

de France, T. XIII., p. 15G.

'88a. (See Article II., '88.)

*'89. Anomalie de l'antenne droite chez Diaptomus c&rtdeus Fisch.,
male. Bull, de la Soc. zool. de France, T. XIV., pp. 38, 39.

North American Species of Diaptomus. 199

'89a. Xote sur les pecbes effectives par M. Ch. Rabot clans les lacs

Euara, Imandra, et dans le Kolozero. Bull, de la Soc. zool. de France,

T. XIV., pp. 100-109.
'89b. Description du Mesochra blanchardi, Copepode nonveau des

Sebkhas algeriennes. Bull, de la Soc. zool. de France, T. XIV.,

pp. 317-321.

'90. (See Article II., '00c.)

'90a. Sur les Entoinostraccs et quelques autres animaux inferieurs
des lacs de l'Auvergne. Rev. des Sci. Nat. Appl.iqu6es, 37 e Ann.,
l re Sem., Xo. 10, pp. 472-181. 10 Fig.

'90b. (See Article 1 1., '90a.)

'90c. (See Article II., '90b.)

'90d. Xote preliminaire sur le systeme nerveux de quelques especes
de Diaplomus. Bull, de la Soc. zool. de France, T. XV., pp. 212-219.

'91. (See Article II.)

'91a. (See Article II.)

'91b. Recherches sur le systeme glandulaire et sur le systeme ner-
veux des Copcpodes libres d'eau douce, suivies d'uue revision des
especes de ce groupe qui vivcut en France. Ann. Sci. uat. zool., T.
XII., pp. 113-270, PI. V.-VIII.

'92. Free Fresh-water Copepoda. Ann. Sci. Xat., Vol. XII., pp. 113-
270; Abstract, Journ Roy. Micr. Soc., 1S92. p. 47s.

'93. Copcpodes recueillis par M. le Dr. Theod. Barrois.en Egypte, en
Syrie et en Palestine (Mars-Juin, 1890). Rev. Biol, du Xord de la
France, 5 e aim., Xo. 10. juillet, 1893. 30 pp., 51 Fig.

'94. Entoinostraccs recueillis par M. E. Modigliani dans le Lac Toba
( Sumatra). Ann. del Mus. Civ. di Storia Nat. di Genova. Ser. II. a ,
Vol. XIV. (XXXIV.), Oct., 1894, pp. 5G5-57S, Fig. 9-14.
[Diaptomus doriai n. sp.]

'95. (See Article II., '95a.)

'95a. (See Article II., '95b.)

'97. Sur quelques Entoinostraccs d'Eau douce des environs de Buenos
Aires. Anales del Mus. Xac. de Buenos Aires, T. V., pp. 321-332,
Fig. 1-0.

[Diaptomus bergi n. sp.]

'97a. Entoinostraccs recueillis par M. leDirecteur Steindacbner dans
les lacs de Janina et de Scutari. Ann. d. K. K. Naturhist. Ilofmus.,
Bd. XII., Heft 1, pp. 03-06, Fig. 1-4.
[Diaptomus steindachneri n. sp.]

'97b. Entoinostraccs de rAmerique du Sud recueillis par MM. U.
Deiters, J. von Ihering, G. W. Miiller et G. O. Poppe. Mem. de
la Soc. zool. de France, T. X., pp. 263-301, Fig. 1-45.

200 Illinois State Laboratory of Natural History.

'97c. Sur deux Entomostraces d'Eau douce recueillis par M. Chaf-
fanjon en Mongolie. Bull. du. Mus. d'hist. nut.. 1897, No. -1. pp.
131-135, Fig. 1-5.

[Diaptomus chaffanjoni n. sp.]

Riickert, J.
*'94. Zur Eireifung bei Copepoden. Merkel-Bonnefs Anat. Hefte,
I. AM., XII. Heft, pp. 261-351, Taf. XX.-XXV.; Abstract, Zool.
Centralbl., II. Jahrg., Xo. 10, pp. 291-295.

Russki.
*'89. Le faune pelagique du lac de Kabane. (French title of Russian
work.) Trav. Soc. imp. des nat. de l'TJniv. de Kasan, T. XIX.
Sars, G. 0.
'62. (See Article II.)
'63. (See Article II.)
'64. (See Article II.)

'86. Crustacea. II. Den norske Nordhavns Expedition 1876-78, pp.
76-79. Christiana.

'89. On some Fresh-water Ostracoda and Copepoda raised from dry

Australian mud. Forh. i Vidensk.-Selskab. i Christiania. pp. 1-77,

PI. I.-VIII. (Pis. I. and II. colored.)
'95. On some South African Entomostraca raised from dried mud.

Vidensk.-Selskab. Skrifter. I. Math.-naturw. Klasse. 1895, Xr. 8,

pp. 1-55. 8 Pis.

[Paradiaptomus lamellatus, n. gen. and n. sp.]

'96. On a new Fresh-water Ostracod. Stenocypris chevreuXi, G. O.

Sars, with notes on some other Entomostraca raised from dried

mud from Algeria. Arch. f. Math, og Naturvid. Kristiania. 27 pp.,

3 Pis.
'97. Pelagic Entomostraca of the Caspian Sea. Extraitde I'Animaire

du Musee Zoologique de 1'Academie Imperiales des Sci. de St.-

Petersbourg, 1897. 7:5 pp., 8 Pis.

Schmeil, O.
'89. t'ber den Diaptomus des salzigen Sees (Diaptonius richardi n. sp.).
Zool. Anz.. XII. Jahrg.. No. 323. pp. UG-GV.).

'91. (See Article II.)

'92. Deutsehlands freilebende Siisswasser-Copepoden. I. TeilrCy-
clopidse. Bibliotheca Zoologica, Ileft 11. 191 pp., 8 Pis.

'94. (See Article II.)

'94a. Einige neue Harpacticidenformen des Siisswassers. Zeitschr.

f. Naturwissensch., Bd. LXVIL, pp. 341-350.
'95. Neue Spaltfusskrebse der Fauna der Provinz Sachsen. Zeitschr.

f. Naturwissensch., Bd. LXVIIL, i>i>- 126-130.

North American Species of Diaptomus. 201

'96. Deutschlands freilebende Susswasser-Copepoden. III. Teil:
Centropagidre. Abt. I. u. II. Bibl. Zool. Heft, 21, Lfg. I. u. II.,
Taf. I.-XIL, 3 Fig. in Text; Abstract, BioL Centralbl , XVI. Bd.,
Nr. 23, pp. 845-847.

'97. Deutschlands freilebende Susswasser-Copepoden. Nachtrag.
Bibl. Zool. Heft 21, Nachtrag, pp. 145-188, Taf. XIII., XIV.

Scott, T.
*'94. Diaptomus serricornis Lilljeborg, in Lochs in Barra and North,
Uist. Ann. Scot. Nat. Hist., Oct., pp. 258, 259.

Scourfield, D. J.
'93. (See Article II.)
'94. Entomostraca and the Surface-film of Water. Journ. Linn. Soc,

Vol. XXV., Zoology, No. 15S, pp. 1-19, Pis. I., II.
'95. A Preliminary Account of the Entomostraca of North Wales.

Journ. Quekett Micr. Club, Vol. VI., Ser. 11., Xo. 37, pp. 127-143,

PI. VIII.
'97. Verzeichniss der Entomostraken von Plon. Forschungsber. a.

d. Biol. Stat, zu Plon, Theil V., pp. 180-1S3. Stuttgart.

Seligo, A.
'90. (See Article II.)

Siebold, C. Th.

*'39. Beitriige zur Naturgeschichte der wirbellosen Thiere. II. Uber
das Begattungsgeschiift des Cyclops castor. Neueste Schrift, Nat.
Ges. Danzig, Bd. III., Heft 2, pp. 36-50, Taf. 2, Fig. 41-44.
(Ubersetzt in: Ann. Sci. Nat. Paris, T. XIV., pp. 26-38, Taf. V.
Nach Giesbrecht.) [Fide Schmeil.]

Sowinsky, W.

'91. (See Article II.)

*'91a. Sur la nouvelle espece du genre Diaptomus, trouvee dans le
lac Kibnoye-Ozero pres de la ville Stawropol. [French title of Kus-
sian article.] Mem. de la Soc. des natural, de Kiew, T. XI., Part I.
4 pp., 1 Fig. in text.

Steck. Th.
'93. Beitriise zur Biolog-ie des s-rossen Moosseedorfsees. Mitt. d.
naturf. Gesellsch. in Bern, Jahrg. 1893, pp. 20-73.

Stuhlinann, F.
'91. Beitriige zur Fauna central-afrikanischer Seen. Zool. Jahrb.,
Abteil. f. System., Bd. V., pp. 924-926.

Szekely, B.
*'82. I'anulmanyok a Diaptomus petefejlodescnek els("» phasisairol a
blastoderma fellepeseig. Kolozsvart.

202 Illinois State Laboratory of Natural History.

Thallwitz, J.
*'91. Die Siisswasser-Calaniden Deutschlands. fTat.Bundschaa.6d.
VI,, pp. 131, 132. Berlin.

Turner, C. H.
'92. (See Article II.)

TTlianin, W. N.

*'74. Cladoceren uud Copepoden eiuiger Seen des centralen Russ-
lands. Schriften d. Gesellsch. v. Freunden der Xaturwissensch.,
etc., zu Moskau, Bd. X., Abt. II., pp. 7S-81.

'75. Crustaceen von Turkestan. Reise A. P. Fedtschenkos in Turk-
estau. [German title of Russian article.] Schrift. de Gesellsch. v.
Freunden der Xaturwisseuseb., etc., zu Moskau, Bd. XL, Abt. VI.,
Copepoden, pp. 22-41, Taf. VI.-X1I.

Underwood, L. M.
'86. (See Article II.)

Vejdovsky, F.

'82. Thieriscbe Organismen der Brunnengevviisser von Prag. 66
pp., 8 Pis. Prag.

Villepoix, R. M. de
'88. (See Article II.)

Vosseler, J.
'86. (See Article II.)
'89. (See Article II.)

'91. Die Krebsfauna unserer Gewiisser. In Zacharias's "Die Thier-
und Prlanzenwelt des Siissvvassers,*' Bd. 1., pp. 323-3S0. 6 Fig. Leip-
zig.

Weber, Max.
'92. ()n the Fresh-water Crustacea of the Indian Archipelago with
Observations on the Fauna of Freshwater in General. Ann. Xat.
Hist., Ser. 6, Vol. XIV., pp. 237-253.

'92a. Die Siisswasser-Crustaceen des Indischen Archipels, nebst Be-
rnerkungen iiber die Siisswasser-Fauna ini Allgemeinen. Zool. Er-
geb. einer Reise in Niederliind, Ost-lnd., pp., 528-571, Taf. XXX.
Leiden.

Westwood, J. O.
*'36. Cyclops. Partington's Cyclopedia. Xat. Hist.

Wierzejski, A.
'82. Materyjaly do fanny jezior tatrzaiiskich. [Materials for the
Fauna of the Karpathian Lakes.] Copepoden. Sprawozd. Kora.
fiz. Akad. Umiej., T. XVI.. pp. 233, 234. Taf. 111.

North American Species of Diaptomus. 203

*'83. Zarys fauny stawow tatrzauskieh. Pamietn. Tow. tatrz., T.
VIII. Krakau.

'87. O. Krajowych skorupiakach z rodziny Calanidae. [On the na-
tive Copepoda of the Family Calanidae.] Kozpr. i Sprawozd.
Wydz. mat.-przyr. Akad. Umiej. Krakau, T. XVI. 13 pp., 1 PI.

'95. Prezeglad fanny skorupiakow galicyjskich. [Review of the
Crustacean Fauna of Galicia.] (See Article II. for citation.)

Wille, N.
'96. Mitteillungen aus der biologisehen Gesellsehaft in Christiania.
Biol. Centralbl., XVI. Bd., Nr. 3, pp. 124-126.

Zacharias, O.
*'85. Studien liber die Fauna des Grossen und Kleinen Teichs irn

Riesengebirge. Zeitschr. f. wiss. Zool., Bd. XLL, pp. 483-51G, Taf.

XXVI.
'87. (See Article II.)
'87a. Znr Entoraostrakenfauna der Umgebung von Berlin. Biol.

Centralbl., Bd. VII., Nr. 5, pp. 137-139.
'87b. (See Article II.)
'88. (See Article II., '88a.)
'88a. Die Tierwelt der Eifelmaare. Biol. Centralbl., VIII. Bd., Nr. 18,

p. 574.
'88b. Uber die geographische Verbreitung des genus Diaptomus.

Biol. Centralbl., VIII. Bd., Xr. 18, p. 575.
'89. Bericht iiber eine Zoologische Exkursion an die Kraterseen der

Eifel. Biol. Centralbl., IX. Bd., Xos. 2, 3, pp. 56-64, 76-80.
'90-91. Uber ein interessantes Kapitel der Seenkunde. Biol. Cen-
tralbl., X. Bd., Xr. 18, pp. 123-128.
'93. Fauna des grossen Ploner Sees. Forschungsber. aus der Biol

Station zu Plon, Teil I., pp. 3-13; Extract, Biol. Centrabl., XIII

Bd., Nr. 11 u. 12, pp. 377-382.
'94. Faunistische Mitteilungen. Fauna des grossen Ploner Sees.

Forschungsber. aus der Biol. Stat, zu Plon, Teil. II., pp. 57-66.
'95. Uber die horizontale und vertikale Verbreitung limnetischer

Organismen. Forschungsber. aus der Biol. Stat, zu Plon. T. III.,

pp. 118-128. Extract Biol. Centralbl., XIII. Bd., Nr. 11 u. 12, pp.

377-382.
'95a. Statistische Mitteilungen aus der Biologischen Station am

grossen Ploner See. Zool. Anz., XVIII. Jahrg., pp. 28, 70, 87, 125?

140, 190, 256, 305, 367, 414, 448.
'96. (Quantitative Untersuchungen iiber das Limnoplankton. 64 pp.

Berlin.

204 Illinois Slate Laboratory of Natural History.

'97. Biologisehe Beobachtungen an den Yersuchsteichen des Schles.
Fischerei-vereins zu Trachenberg. Forschungsber. a. d. Biol. Stat.
zu Plon, Theil V., pp. 10-28. Stuttgart.

Zaddach, E. G.
'44. Synopseos Crustaceorum Prussicorum Prodromus. Dissertatio
Zoologica. 47 pp. Regiomonti (Konigsberg).

Zenker. W.
'54. (See Article II.)

'54a. System der Crustaceen. Arch. f. Naturgeseh. XX. Jabrg.,
Bd. I., pp. 108-118.

'54b. Critik der Erichson'schen Gliedmassentheorie. Arch. f. Na-
turgesch., XX. Jahrg., Bd. I., pp. 118-138.

Zograf. N.
*'96. Essai duplication de rorigine de la faune des lacs de la Rus-
sie d'Europe. Compt. rend, des seance du troisieme congres internat-
de Zool.. Leyde, 16-21, sept., 1895, pp. 183-195. Leyde. Abstract,
Zool. Centralbl., III. Jahrg., No. 14, pp. 481-483.

Zopf. W.
'95. Conn's Hamatochrom ein Sammelbegriff. Biol. Centralbl., XV.
Bd., Nr. 11, pp. 417-427.

Zschokke, F.

'90. (See Article II.)
'90a. (See Article II.)
'91. (See Article II.)

*'91a. Die zweite zoologische Excursion an die Seen des Rhiitikon.
YerbandL Xaturf. Gesellsch. Basel, Bd. IX.. 2 Teil, pp. 425-508;
Abstract, Journ. Roy. Micr. Soc, 1892, p. 194.

'94. Die Tierwelt der Juraseen. Rev. Suisse de Zool. et Ann. du

Mus. d'hist. nat, de Geneve, T. II., Liv. II.. pp. 349-376, PL X1Y.
'94a. Die Fauna hoch gelegener Gebirgsseen. Ein Beitrag zur

Kenntniss der Yertikalen Yerbreitung niederer Tiere. Yerh. d.

Naturf. Gesellsch. in Basel, Bd. XL, Heft 1, pp. 36-133, Taf. I.
'95. Die biologische Station zu Plon nach den Forsehungsberichten.

Teil II. u. HI. Biol. Centralbl. XY. Bd., Nr. 10, pp. 408-415.

Nortlt American Species of Diaptomus. 205

EXPLANATION OF PLATES.

Plate XXI.

Fig. 1. Diaptomus sicilis, fifth feet of male. X '280.

Fig. 2. Fifth feet of female of same (minus one outer ramus). X 280.

Fig. 3. Last thoracic segment and abdomen of female of same. X 140.

Plate XXII.

Fig. 1. Diaptomus piscina', fifth feet of male.

Fig. 2. Fifth foot of female of same (Portage Slough specimen). X 280.

Fig. 3. Last thoracic segment and abdomen of female of same. X 140.

Fig. 4. Fifth foot of female (Yellowstone Park specimen). X 280.

Plate XXIII.

Fig. 1-5. Diaptomus sanguineus, second basal segment of right fifth foot

of male. X 210.
FiG. 6-8. Terminal segments of right male antenna of same. X 210.

Plate XXIV.

Fig. 1, 2. Diaptomus sanguineus, first abdominal segment of female, seen

from the side. X 110.
Fig. 3. Last thoracic and first abdominal segments of female of

same. X 110.
FiG. 4. Fifth feet of male of same. X 210.
Fig. 5, G. Dorsal outline of female of same, showing hump. X 110.

Plate XXV.

Fig. 1, 2. Diaptomus sanguineus, fifth foot of female. X 240.
Fig. 3, 4. Right fifth foot of male of same. X 210.
Fig. 5. Fifth feet of male of same (variant). X 210.

Plate XXVI.

Fig. 1. Diaptomus shoshone, last thoracic segment and abdomen of

female. X 80.
FiG. 2. Fifth foot of female of same. X 280.
FiG. 3. Abdomen of male of same. X 128.

Plate XXVII.

Fig. 1. Diaptomus lintoni, fifth feet of male. X 280.

Fig. 2. Diaptomus pallidas, fifth foot of female. X 280.

Fig. 3. Fifth feet of male of same. X 280.

Fig. 4. Diaptoimis albuquerquensis, fifth feet of male. X 400.

206 Illinois State Laboratory of Natural History

Plate XXYIII.

Fig. 1. Diaptomus reighardi, fifth feet of male. X 400.
Fig. 2. Diaptomus stagnalis, right antenna of male. X 80.

Plate XXIX.*

Fig. 1. Diaptomus oregonensis, fifth feet of male. X 240.

Fig. 2. Fifth foot of female of same. X 300.

Fig. 3. Diaptomus signicauda, fifth feet of male. X 200.

Fig. 4. Terminal segments of right antenna of male of same. X 200.

Fig. 5. Fifth foot of female of same. X 200.

Fig. 6. Last thoracic segment and abdomen of female of same. X 100.

Plate XXX.*

Fig. 1. Diaptomus franciscanus, last thoracic segment and abdomen

of female. X 40.

Fig. 2, Terminal segments of right antenna of male of same. X 200.

Fig. 3. Fifth pair of feet of male of same. X 200.

Fig. 4. Fifth foot of female of same. X 200.

Fig. 5. Diaptomus minut'us, fifth foot of female. X 300.

Fig. 6. Fifth foot of male of same. X 300.

Fig. 7. Terminal segments of right antenna of male of same. X 300.

Fig. 8. Last thoracic segment and abdomen of female of same. X 250.

Plate XXXI.

Fi<;. 1.* Diaptomus trybomi, terminal segments of right male antenna.

X160.
Fig. 2.* Last thoracic segment and abdomen of female of same, seen

from right side. X 96.
Fie. 3. The same, seen from above. X 140.
Fig. 4.* Fifth pair of feet of male of same. X 210.
Fig. 5.* Fifth foot of female of same. X 240.

Plate XXXII.

Fig. 1. Diaptomus ashlandi, fifth pair of feet of female (a variant).

X210.
Fig. 2. Fifth foot of female of same. X 240.
Fig. 3. Fifth pair of feet of male of same. X 240.
Fi<;.4. Anterior fifteen segments of right antenna of male of same.

X240.

*After de Uuerne and Richard, '89b.

North American Species of Diaptomus. 207

Plate XXXIII.

Fig. 1. Diaptomus mississii>pie7isis, last thoracic segment and abdomen

of male. X 256.
Fig. 2. Fifth foot of female of same. X 256.
Fig. 3. Fifth pair of feet of male of same. X 256.
Fi<;. 4. Abdomen of female of same seen from below (Prof. Marsh's

specimen). X 256.

Plate XXXIV.

Fig. 1. Diaptomus clavipes, right fifth foot of male (inner ramus want-
ing). X 280.
Fig. 2. Right antenna of male of same. X 140.
Fig. 3. Fifth foot of female of same. X 400.

Plate XXXV.

Fig. 1. Diaptomus clavipes, fifth feet of male. X 280.

Fig. 2. Last thoracic segment and abdomen of female of same. X 140.

INDEX.

(Synonyms
Amphaskandria, 102.
Candacidse, 104.

( lentropagulge, 97, 101, 102. 103.
Centropagiria, 103.
Cyclops, 100, 100, 141.
Cyclops, 97, 10G, 132.
tongicornis, I'M).
Cyclopsina, 97,105.
Diaptomus, 102, 103, 105.

albuquerquensis, 98, 113, 115,

146, 176, 183.
ambiguus, 177.
armatus, 133, 135, 136.
ashlaudi, 9S, 100. Ill, 120,124,

158, 167, 183.
bacillifei-,107.
birgei. 99. 108, 117, 172.
caroli. 181.
castor, 98, 106.
castor, 130.

.•lavipes,98,10S,119,127,178,184
cceruleus, 107.
deitersi, 99.
driesehi, 99.

eiseni, 98,110,115, 162,166,183.
franciscanus, 98, 110. 118, 132,

160.166,182,183.
fresnanus, 176, 178.
gibber, 99.
giganteus, 138.
gracilis, 98, 173, 182.
graciloides, 98.
incongriiens. 99.
kentuckyensis, 97, 130, 132.
leptopus, 97, 112, 117, 125, 127.

130, 135, 181, 182.
lintoni, 113418,1 27,134,160,182
longicornis, 132.

var. leptopus, 130, 132.
var. similis, 132. 162. 182.
minnetonka, 133, 135, 136, 138.
lninutus, 98, 106. Ill, 116, 129,

134, 156. 183.
mississippiensis, 98, 109, 122,

149,173,184.
novarnexicanus, 99, 111. 116,

149, 183.
oregonensis, 109, 119, 124.151,
169, 171, 183.

in Italics.)
Diaptomus — continut <L

pallidus, 100, 108, 121, 124, 137,
144, 156. 183.
var. sirilis. 122.
piscinae, 98, 109.116,118, 125,

127,181,182.
reighardi, 98,109, 121. 169,1S4.
roubaui, 166.
salinus. 99.
sanguineus. 97, 112, 117, 12&,

133, 160, 166, 183.
serricornis, 162.
shosbone.H0.116,141.164.1S3.
sicilis, 97, 100, 111. 121, 122.
145,155,169,182.
var. imperfectus, 124, 158, 167,
169.
siciloides, 98, 100, 114, 121, 124,

137, 146, 154. 157, 165,
166,181,182.183.

signicauda, 98, 114. 120, 157,

159, 160, 164,183.
signicaudatus, 164.
similis, 132, 182.
stagnalis, 97, 113, 115. 129, 136,

138. 141,142.164,183.
trybomi,98.112.120,158.166.183
tyrrelli, 99, 108, 119, 160, 176,

184.

wierzejskii, 107.

zachariasi, 99.
Epischura, 97, 102, 103, 166.

nevadensis. 98. 168.

nordehskiuldi, 9S.
Glaucea, 97, 105.
G ymnoplea. 102.
Heterarthrandria, 102.
Heteroebatina. 104.
Heterocope. 99.
Leuckartiiua, 104.
Limnoealanus, 102, 104.

sinensis. 99.
Monoculus, '.)7. 105.
Osphranticum, !)7, 102,104.
Podoplea, 105.
Pontellida', 102.
Temorella, 99.
Teniorina, 103.
Volvox, 141.

Plate XXI.

Plate XXII.

Plate XXIII.

Plate XXIV.

Plate XXV.

Plate XXVI.

If | 1

' \

Plate XXVII.

Plate XXVIII.

Plate XXIX.

Plate XXX.

1 \ \ j ;

Plate XXXI.

Plate XXXIL

Plate XXXIII.

Plate XXXIY.

Plate XXXV.

BULLETIN

OF THE

Illinois Qtate Laboratory

OF

NATURAL HISTORY,

Urbana, Illinois.

VOLUME V.

ARTICLE IV — THE NORTH AMERICAN CENTROPAGID.E
BELONGING TO THE GENERA QSPHRANTICUM, LIM-
NOCALANUS, AND EPISCHURA.

By FREDERICK WILLIAM SCHACHT, B. S.

Illinois State Laboratory of Natural History,
URBANA, ILLINOIS.

1898.

State Laboratory of Natural History.

LABORATORY STAFF.

Professor Stephen Alfred Forbes, Ph. D„

Director of State Laboratory and State Entomologist.

Charles Arthur Hart,

Systematic Entomologist and Curator of Collections.

Frank Smith, A. M.,

Assistant Zoologist.

Charles Atwood Kofoid, Ph. D.,

Zoologist, and Superintendent of Biological Station.

Ernest Browning Forbes, B. S.,

Entomo logica I Ass istant.

AVallace Crah;, B. S.,

Zoological Assistant.

Mary .Iane Snyder,

Secretary.

Henry Clinton Forbes.
Business Agent and Librarian.

Lydia Moore Hart,
Artist.

Article IV. — The North American Centropagidce belonging
to the Genera Osphranticum, Limnocalanus, and Epis-
chura* By Frederick William Schacht, B. S.

INTRODUCTION.

■

In Article III. of this Bulletin the writer discussed the
North American species of Diaptomus, and in the present
paper, in furtherance of the same purpose, the genera Os-
phranticum, Limnocalanus, and Epischura arc treated. In
the introduction to the former article was given a short
account of the work of writers on the Eutomostraca now
included in the family Centropagidce, especially those genera
found in North America. No reference is made there to the
genera Heterocope and Eurytemora, since at that time I re-
garded the presence of these two genera in North America as
rather doubtful.

The only statement that Heterocope was ever found on this
side of the Atlantic is made by Cragin ('83) t. After an
enumeration of the genera of fresh-water Oopepoda he says :
" Of these eleven genera, four — Diaptomus, Limnocalanus,
Cyclops, and Canthocamptus — have been recorded as common
to the Old World and the New. I add Heterocope on the
authority of my friend, Mr. William Patten, who informs me
that a species is common in Watertown, Massachusetts."
This evidence is not sufficient to justify the treatment of the
genus in this paper.

In regard to Eurytemora (=Temora Temorella) I was per-
haps overhasty in my conclusions, but it being now too late
to remedy the omission, the following statements must
suffice. In his "Final Tieport" Herrick ('84) notes the
occurrence of Temora affinis Poppe in the rivers flowing into
the Gulf of Mexico as well as in the brackish waters into
which these rivers flow. In the "Crustacea of Alabama"
('87) he notes, under the name of Temorella ajjinis, a species
which according to his statement is the same. The figures of

-This paper was accepted by the Faculty of the University of Illinois June 1.
1898, ;is ii thesis for the degree of Master of Science in /oology.

(The parenthetical figures in the text of this paper refer usually to the bibliog-
raphy of Article III., which is. however, supplemented bv an additional list appended
to this discussion.

226 Illinois State Laboratory of Natural History.

the species in question differ, however, so considerably in
these two articles that, as Schmeil ('98) says, nothing certain
can be said of this species until Herrick declares himself as to
which of the two sets of drawings are correct. Schmeil regards
Herrick's form as possibly a new species. The recent dis-
covery of a new species of this genus, Kurt/femora herdmani
I. C. Thompson and A. Scott, in the St. Lawrence River and
Gulf removes all doubt as to the presence of the genus in
American waters.*

Of the three genera treated in this paper, Osphranticuni,
containing a single species, &&& Epischura, containing threei ,
are, so far as now known, confined strictly to North America
and are strictly fresh- water in their habitat. Osphranticum
is ordinarily found in shallow or stagnant lakes and ponds
(Forbes] or in running water (Herrick), while Epischura
occurs, as a rule, in deep clear lakes. The genus Limnocalanus
is peculiar in its habitat. One of the two species, L. sinensis
Poppe, from China, is, so far as known, a strictly fresh-water
form, while the other, L. macrurus Sars, although found as
yet in America in freshwater only, occurs in Europe and Asia
in both fresh- and salt-water lakes and in the ocean. Since
there are only these two species known, it was thought best
to treat both in this paper. L. grimaldii de Guerne is re-
garded by the writer as a synonym of L. macrurus Sars^, for
reasons given in the discussion of the latter species.

A brief discussion of the structural similarities and differ-
ences indicative of the relationships of the genera Osphranti-
cum, Limnocalanus, Diaptomus, and Epischura may properly
precede this paper, special attention being given to characters
which are regarded as of generic or specific value.

Giesbrecht, in his "Monograph" ( ,( .>2), gives special rank
to the structure of the first pair of antenna- as a distinguish-

■M'e "On the Plankton collected continuously during two Traverses of the North
Atlantic in the Summer of 1897; with Descriptions of New Copepoda: and an Ap-
pendix on Dredging in Puget Sound." By W. A.. Herdman, I. C. Thompson, and An-
drew Scott. Trans. Liverpool Biol. Soc, Vol. XII. (1897), p. 79.

fE.fluviatilis Herrick is not considered one of these.

i'l'lie Zoologisch.es C'entraibfatt (Jahrg., 111., pp. 4si 183J contains a review of an
article by X. Zograf entitled " Essaid'Explication de L'origine de la Faune des lacsde
la Russie ii' lairope" in which a reference occurs to /.. mad-onyx G. <». S. This is
probably an error, since it is the only reference toaspecies of that name which I
have hem able t>> find.

North American Centropagidce. 227

ing character in the Copepoda. If this be taken as a basis
of classification here, Osphranticum, with its 2 3 -segmented
antennae, would form a group by itself, while Limnocalanus,
Diaptomus, and Epischura, with their 2 5 -segmented antennae
would constitute another group.

Osphranticum seems to be the most primitive of the Amer-
ican Centropagidce, the fifth legs especially being less differ-
entiated than in any of the other genera. This is particularly
true of the female, in which all of the legs are biramose, each
ramus consisting of three segments. In the male the left
fifth leg is similar to the preceding legs, but the right one has
a two-segmented outer ramus, the second segment being ap-
parently formed by the coalescence of the second and third
segments. In both sexes the inner rami of all the pairs of
legs are alike.

Limnocalanus apparently approaches most closely to Os-
phranticum, the fifth pair of legs of the female being very
similar in general structure to those of Osphranticum, as is
perhaps most strikingly illustrated in the case of L. macru-
rits Sars and . labronectum Forbes. In Limnocalanus both
rami of the four anterior pairs of legs in both sexes are three-
segmented and but slightly modified, as are also those of the
fifth pair of legs of the female; but in the latter the second
segment of the outer ramus is produced on the inner margin
into a hook-like process, as in Osphranticum. The inner
rami of the fifth pair of legs of the male are still three-
segmented and similar to those of the preceding legs, but the
outer rami are modified and are two-, or indistinctly three-,
segmented.

Diaptomus is perhaps next in respect to modification.
In this genus all the legs are biramose, but the first pair con-
sists of a three-segmented outer, and a two-segmented inner,
ramus. The following three pairs have both rami three-seg-
mented. In the female the fifth pair of legs has a two- or,
more rarely, three-segmented outer ramus, and a one- or,
occasionally, two-segmented inner ramus. In the male the
inner ramus is one- or, rarely, two- segmented, while the outer
ramus of the right leg is three-segmented and that of the left
leg two- segmented.

228 Illinois State Laboratory of Natural History.

In Epischura, as in the other three genera, the cephalotho-
rax is six-segmented. All of the swimming legs have a
three-segmented outer, but a one-segmented inner, ramus.
In the female the inner ramus has entirely disappeared in
the fifth pair of legs, and the outer ramus is two-segmented. .
In the male also the fifth pair of legs are without inner rami,
and the outer ramus of the right leg is two- or three-segmented,
that of the left leg three-segmented. A peculiarity of this
genus is the modification of the abdomen of the male into a
clasping organ. The abdomen of the female is also modified
in at least one species (lacustris).

So much for the relationships indicated by the structures
considered. According to the above, Osphranticum must be
regarded as the most primitive form, Epischura as the most
modified, and Limnocalanus and Diaptomus as occupying an
intermediate position. I think that the mass of charac-
ters will support this statement, although there are other
characters which would lead one to doubt somewhat its
correctness. For example, in Osphranticum and Diaptomus
the females carry the eggs in an egg-sac, while in Limnocal-
anus and Epischura they do not. In Osphranticum, I>iaj>tn-
mus, and Epischura the spermatophore persists tor some time ;
but I have not seen a single female Limnocalanus with a
spermatophore, although according to Giesbrecht the fertili-
zation by means of a spermatophore is about the only charac-
teristic which all Copepoda have in common.*

The material at my command for the preparation of this
paper has been complete; that is to say, I have had speci-
mens of all the known species of the genera treated, ami
access to the most recent literature. The collections exam-
ined belong in great part to the Illinois State laboratory of
Natural History, in part to Prof. Frank Smith, of the Univer-
sity of Illinois, and in part to myself. The following localities
are represented : Norway, the Caspian Sea, Lake Sitai and
the Whangpoo River in China, Newfoundland, and the Stati -

* "The sexually mature individuals are to some extent mi transformed by para-
sit ism that unless the fertilization by menus of spermatophores be excepted they seem
tn have no characteristic common to all which would at the same time distinguish the
(inter Copepoda from the other orders of Entomostraca." (Giesbrecht, '5)2. p. i

North. American Centropagidce. 229

of Illinois, Indiana, Ohio, Michigan, Washington, Oregon,
Montana, Wyoming, Idaho, and Nevada.

Through the kindness of Professor Smith I was able to
examine collections from Lake George and Lake James in
Steuben County, Ind., in which I found specimens of Epis-
chura lacustris and Diaptomus oregonensis. Mr. Chancey
Juday, Curator of Collections, University of Indiana, kindly
sent me collections from Tippecanoe Lake, Eagle Lake, and
Turkey Lake, in Indiana, in which occurred Epischura lacus-
tris, Diaptomus sicilis, D. oregonensis, and 1 >. siciloides. I also
acknowledge my indebtedness to Prof. G. 0. Sars, who kindly
furnished me with specimens of Limnocalanus grimaldii, thus
enabling me to compare them with L. macrurus — also fur-
nished by him to the Illinois State Laboratory of Natural
History; to Herr S. A. Poppe, for specimens of Limnocalanus
sinensis', to Professor Lillejeborg for Epischura nevadensis;
and to Dr. C. A. Kofoid, Superintendent of the Illinois Biolog-
ical Station at Havana, to whom I owe thanks for his many
kindnesses during my stay at the Station in July, 1896, and
while at the University.

No illustrations accompany this paper, since the species
treated may be identified by figures already published.

OSPHRANTICUM Forbes.

Osphranticum, Forbes. '82a, p. 645.
Potomoichetor* , Herrick, '82, p. 23.

< Osphranticum, Herriek, "84, p. 134.
Osphranticum, Herrick, "87, p. 12.
Osphranticum, de Gnerne et Richard, '89b. p. 149.
Osphranticum, Herrick and Turner, '95, p. 85.

Cephalothorax compact, six-segmented, the first two seg-
ments continent above, the last segment produced into a
bluntly-rounded lobe on each side. Abdomen (furca in-
cluded) composed of five segments in the female, of six in
the male. Furcal rami hairy on the inner margins ; armed
with five plumose seta3, the second from within the longest,
and with a delicate smooth seta on the inner margin of the

*Spelled Potamoichetor in Ilerrick's subsequent references.

230 Illinois State Laboratory of Natural History.

dorsal surface. First pair of antennae 23-segmented : right
male antenna geniculate between the 18th and 19th seg-
ments, and the 19th and 20th segments ankylosed. Second
pair of antennae, mandibles, and first, second, and third
pairs of maxillae as in Diaptomus, but stouter. All the swim-
ming legs biramose, with three-segmented inner and outer
rami; armed with stout seta?. In the female the legs of the
fifth pair are alike, biramose, the rami three-segmented, the
inner ramus the shorter. Fifth pair of legs of male bira-
mose, dissimilar. Both rami of left leg three-segmented, the
inner ramus the shorter. Outer ramus of right leg two-
segmented, the inner three-segmented and like the inner
ramus of the left leg. Egg-sac obovate.

Osphranticum labronecturn Forbes.

Osphranticum labronecturn, Forbes, '82, p. 645, PI. VIII., Fig. 24. 28.
29; PL IX., Fig. 1, 2, 4. 5, 7, 9.

Potomoichetor* fucosus, Herriek, '82. p. 224, PI. II., Fig. 12-14: Pi.

III., Fig. 1-8. 13. 14.
Osphranticum labronecturn, Herriek, *84. p. 134, PJ. Q2, Fig. 1-8. 13. 14.
Osphranticum labronecturn, Herriek, "87. p. 12.

Osphranticum labronecturn, de Guerne et Richard. 89b, p. 149, Fig. 1 . 2.
osphranticum labronecturn, Herriek and Turner, *9">, p. 86. PL XII..

Fig. 1-8, 13, 14; PL LIX., Fig. 7, 8.

Of medium size, body compact, widest before the middle.
Ceplialothorax composed of six segments decreasing gradu-
ally in length from before backward ; first two segments con-
fluent above, the last segment slightly produced at the angles
into bluntly-rounded points, but unarmed. Abdomen (furca
included) composed of five segments, decreasing in length
from before backward. Furcal rami, however, slightly longer
than the preceding segment and about twice as long as wide ;
hairy on the inner margin and armed with five long plumose
seta? of which the second from within is the broadest and
longest, the middle one being next in length, and the other
three subequal ; dorsal surface of each ramus armed near
the inner apical angle with a delicate smooth seta. Abdo-
men of male composed of six segments : the first shorter

■Spelled Polamoichetor in Merrick's subsequent refereints.

North American Centropagidce. 231

than any of the others except the fifth, which is the shortest :
the second, third, and fourth segments decreasing in length
in regular order ; the second slightly shorter than the furcal
rami, which are armed as in the female.

Antenna? 23-segmented, extending about to the end of the
cephalothorax, or barely surpassing it. Eight male antenna
geniculate between the 18th and 19th segments; 19th and
20th segments ankylosed; six segments preceding the genieu-
lation rather thickly swollen; penultimate segment produced
at the inner apical angle into a broad bluntly-rounded process
extending slightly beyond the end of the segment.

Fifth pair of legs of male biramose. Second basal segment
of right leg armed above the middle of the outer margin with
a delicate hair slanting upward. First segment of outer
ramus slightly longer than the width at the base, irregularly
trapezoidal, the outer margin forming the longest side ; armed
at the outer apical angle with a stout spine about as long as
the segment itself and provided on ea-ch margin with a nar-
row hyaline lamella; just within this, another very minute
spine. Second segment irregular in form, the proximal third
subquadrate, about as wide as the preceding segment, pro-
duced at the inner apical angle in the form of a rather large
cushion-like pad sparsely covered with delicate hairs ; distal
two thirds subquadrate, about half as wide as the proximal
third, provided on the inner margin with delicate hairs, and
armed a short distance above the middle of the outer margin
with two spines, one large and one small, similar to those on
the preceding segment; apex of segment armed with three
spines fully as long as the segment itself, the outer two
straight, the inner curved inward slightly, and each of them
provided with a hyaline lamella, the edges of which seem to be
plumose. Just posterior to the inner apical seta is a short
slender spine.

First segment of inner ramus of right leg irregular in form,
about as long as wide, provided on the inner margin with a
few fine hairs. 'Second segment slightly wider than the pre-
ceding, barrel-shaped, and slightly longer than wide; pro-
vided on the inner margin with a few fine hairs, and at the

v 28'2 Illinois Stale Laboratory of Natural History.

outer apical angle with a long delicate plumose seta. Third
segment slightly narrower than the second; margins sulcate,
armed with six subequal plumose seta? similar to the seta on
the preceding segment, of which three are apical, two are on
tin' outer margin, and one is on the inner. The seta' are so
placed as to form two groups of three each.

Basal segments of left fifth leu like those of right leg. First
segment of outer ramus similar to the corresponding segment
of the outer ramus of the right leg and similarly armed, hut
not quite so broad. Second segment subquadrate, about one
and a half times as long as wide; outer apical angle armed
as in the preceding segment; inner margin provided with a
few delicate hairs. Third segment considerably narrower
than the second and slightly shorter; armed at the apex with
two lamellate seta j and a short sharp spine. Inner ramus
like that of right leg.

Fifth pair of legs of female biramose. Second basal seg-
ment provided on the- outer margin, a short distance above
the middle, with a delicate hair slanting upward. First seg-
ment of outer ramus subquadrate, slightly broader than long ;
armed at the outer distal angle with a long lamellate spine;
and on each side of this with a very minute smooth spine.
Second segment somewhat shorter and narrower than the
preceding ; armed at the outer distal angle like the first seg-
ment, except that the inner of the small spines is wanting ;
inner apical angle produced into a long, moderately stout
lamellate hook, shaped about like the blade of a pruning
knife ; both margins provided with a few fine hairs. Third
segment slightly longer than the second, about twice as long
as wide; armed at the outer apical angle with a plumosely
lamellate spine almost as long as the segment itself, and at the
apex with two similar subequal spines (about twice the length
of the lamellate spine) and a short smooth spine; outer mar-
gin provided with a few long tine hairs ; inner margin sulcate
and armed with four slender subequal plumose seta- about as
long as the segment.

Inner ramus of fifth leg of female three-segmented, the
first segment irregular in' shape, with a somewhat projecting

North American Centropagidce. 233

inner apical angle. Second segment sub quad rate, about one
and a half times as long as wide ; armed at the outer apical
angle with a plumose spine almost twice as long as the seg-
ment, and on the inner margin with a few fine hairs. Third
segment slightly longer and narrower than the preceding;
irregularly triangular, with sulcate margins and truncate
apex ; armed on the outer margin with two long, slender, plu-
mose setae, at the apex with two similar setae and a short
smooth spine, and on the inner margin with one seta similar
to those already mentioned and one shorter lamellate seta,
and provided on the upper half with a few tine hairs.

Length of female, 1.703 mm.; that of male, 1.362 mm.

The above description was prepared from specimens col-
lected in the summer of 1896 at the Illinois Biological
Station, at Havana, 111. ; from type specimens; and from
other State Laboratory material collected at various times
and places, mostly in Illinois.

The single species of this exclusively North American
genus was first described by Herrick in a paper read before
the Minnesota Academy of Sciences in 1879, but which,
owing to a fire, was not published until 1882. The descrip-
tion then appeared, under the name Potomoichetor fucosus, in
the Tenth Annual Report of the Geological and Natural
History Survey of Minnesota (Herrick '82). This Report
was not distributed, however, until after the August number
of the "American Naturalist" appeared, which contained the
description of Osphranticum labronectum by Forbes ('82).

De Guerne and Richard, in their "Revision" ('89b), pub-
lish the best figures of this species. Although not strictly
correct in every particular, the omissions are of minor im-
portance, as may be seen by the following enumeration of
them. In the fifth legs of the female the hair on the second
basal segment, the small spines at the outer apical angles of
the segments of the outer ramus, the hairs on the outer
margins of these segments, and the lamella of the hook at
the inner apical angle of the second segment of this ramus
are not figured. The third segment of the inner ramus is
not quite correct. Here the hairs on the inner margin, the

234 Illinois State Laboratory of Natural History.

lamella on the upper spine of this margin, and the small
spine on the apex of the segment are all omitted, hi the
figures of the fifth pair of legs of the male, the small spines
at the outer apical angles of the segments of both outer rami,
the spine at the inner apical angle of the last segment of the
right outer ramus, and the hairs on the inner margin of the
first segment of both inner rami are wanting.

Although this species is widely distributed, — having been
found in Alabama, Illinois, Minnesota, Oregon, and Wyo-
ming, — no differences sufficient to establish even a new
variety have been found in specimens from these localities
so widely separated and so varied in character. Herrick, in
his papers, states that all the specimens examined by him,
from Alabama to Minnesota, had 24-segmented antennae.
Forbes found the antennae 23-segmented, de Guerne and
Richard, who examined specimens sent to Poppe by Forbes,
agreed with him, and the writer also found the antenna? of all
the specimens lie examined to be 23-segmented. The speci-
mens collected by Dr. Forbes in April, 1877, and described in
1882, were uniform pale brown; those collected by the
writer at Havana, 111., in July, 1896, were hyaline or opal-
escent white; while a single male found in June, 1897, at
Urbana, 111., in a temporary pool, was bright scarlet through-
out, and hardly to be distinguished from the specimens of
I), sanguineus among which it was found. Herrick has found
Osphranticum in "estuaries of running water," and says that
according to his observations it prefers such localities. The
writer's observations tend to confirm Forbes's statement
that it prefers swamps and pools, or at least quiet or stag-
nant water. At the Biological Station at Havana, during
the summer of 1896, a single specimen was captured in the
Illinois River, in midstream, while in Quiver Lake, in a mat
formed of Ceratophyllum and Lemna in a stagnant portion
near shore (substation C), they were comparatively numer-
ous, though not occurring in any such numbers as either
I >i<t]>h>nni* or Cyclops. In fact, in none of the collections
examined were they at all common.

Prof. Forbes, in connection with the original description,

North American Centropagidce. 235

makes a remark in regard to the "steady movement in the
water," and this is all, to my knowledge, that has been said
about the habits of Osphranticum. The following statements,
gathered from observation of a number of specimens kept
for some time in a large flat dish may therefore be of interest.
Their movements in the water are very different from the
short jerky springs of ( 'yclops, and they differ also from those
of Diaptomus in that they are more regular. The motions
of these three genera might perhaps be expressed by tele-
graphic symbols as follows : Cyclops, - -; Diapto-
mus, - -; and Osphranticum,- —
— . Osphranticum swims equally well on the

dorsal or ventral surface, seeming, however, to prefer the
former position. As in Diaptomus, the anterior end is ele-
vated in swimming, and the antennae are actively employed.
Sometimes it will turn backward somersaults, going over and
over in the water, but I have seen this done only when indi-
viduals were swimming on the back. When startled they
would dart to the bottom, hide for an instant under a bit of
debris, and then make another dash, repeating the perform-
ance until they deemed themselves out of danger.

Since 0. labronectum is the only species known, no key
will be required.

L.IMNOCALANUS G. 0. SaRS.

Limnocalamis, Sars, '62, p. 226.
Centropages, cle Guerne, '86, pp. 276-2S5.

Body long and narrow, the front armed with two book-like
processes. Cephalothorax widest at the middle, composed
of six well-defined segments ; last thoracic segment not pro-
duced laterally but slightly projecting posteriorly and armed
on each side with a minute blunt spine. Abdomen slender;
in the female composed (furca included) of four (macrurus)
or five (sinensis) segments. Furcal rami very long, hairy on
the inner margin ; armed with five stout plumose setae (the
second from within the longest), and one slender seta (plu-
mose in sinensis), shorter than the rest, on the dorsal surface,

236 Illinois State Laboratory of Natural History.

near the inner margin and opposite the outermost of the
other setae.

First pair of antenna 1 shorter than the body, 25-segmented,
the hist segment very small. Eight male antenna geniculate
between the 18th and 19th segments, each of which is armed
with a hyaline lamina. Outer ramus of second pair of
antennae seven-segmented* and armed with very long setae.
Mandibles produced at the inferior extremity into nine
teeth, of which the outer two are longer than the rest, the
inner two slender and setiform ; palpus long and narrow,
three-segmented, the last two segments very short, outer
ramus small, armed with long seta?. First pair of maxillae
about as in Diaptomus. Second pair of maxilla; robust,
eight-segmented, the last segment produced into long stout
claws; margins otherwise sparsely hairy: the falcate apex
bare or' armed with very small dense spines. Maxillipeds
seven-segmented, much elongated and narrow, directed for-
ward, and armed with numerous long seta?.

All the swimming legs biramose. Both rami of the four
anterior pairs of legs three-segmented, the inner shorter than
the outer.

Outer ramus of fifth pair of legs of female three-segmented ;
;i rmed within, on the second segment, with a very strong,
curved, hook-like process. Inner ramus as in the other legs.

Outer ramus of right fifth leg of male two- (sinensis) or
indistinctly three- (macrurus) segmented, the second segment
produced into a stout hook-like process. Outer ramus of
left fifth leg two-segmented, the second segment armed with
a slender digitiform process. Inner rami three-segmented,
alike, and similar to £hose of the preceding pair (macrurus),
or differing from one another {sinensis). Eye single, near
the lower margin of the head.

This genus was established by Dr. Sars in 1802 to receive

*The parts of the generic description referring to the structure of the second
pair of antennae, the mandibles, maxillae, maxillipeds, and the swimming legs are
compiled from sars ("62 ami ''.i7i. Nordqvisl ('88), and de Guerneand Richard ('89b .
In regard to the second pair of antennae of macrurus the writers mentioned state
that the outer ramus is seven-segmented, anil Nordqvisl says further that the suture
between the second and third segments is indistinct, and figures the antenna with six
segments. Sars ("97) says of grimatdii that the outer ramus is six-segmented and so
figures it. After careful examination. I find no difference in the second pair of an-
tenna' of macrurus nn<\ grimaldii, the segmentation being equally distinct, each of
the four spines between the second and last segments markim; a segment.

North American Centropatjidce. 237

a fresh-water centropagid closely resembling the marine
genus Calanus, and until 1889 L. nun-rums was the only rep-
resentative known. In that year Poppe described (de Guerne
et Richard, '891)) a new species, L. sinensis, from China.
The latter, so far as now known, is a purely fresh- water form,
and L. macrurus was at first so regarded, but in Asiatic and
European countries it has been found to occur in both fresh
and salt water, — in America it has as yet been found only in
fresh water, — and further search may show that L, sinensis,
too, is common to both. L. macrurus is the only American
representative of the genus, but it was deemed best to in-
clude sinensis in this paper, thus making the revision of the
genera treated complete.

As already stated, the genus is represented by only two
species, macrurus and sinensis. The former is common to
America, Europe, and Asia, having been found in the river
J ana (in East Siberia), in the Caspian Sea, in the Arctic
Ocean, in the lakes of northern Norway, Sweden, and Fin-
land, and in the deeper northern lakes of North America;
the latter, sinensis, has been found only in eastern China.

Marsh, in his "Limnetic Crustacea of Green Lake" ('97),
records some observations on the habits of Limno calanus,
and states that it is repelled by bright light and high tempera-
tures, and hence performs diurnal migrations which are more
pronounced in cold weather. It seems to have two periods
of maximum occurrence, May and November, but is found at
all times, although never very abundantly. In March and
April most of the individuals are immature.

To my knowledge Limno calanus has never been found with
an egg-sac, differing in this respect from Ospliraniicum and
Diaptomus but agreeing with Epischura. The spermatophore,
a slender tubular structure, adheres to the female for a con-
siderable time after attachment.

From a practical and economic standpoint Limnocalanus
is of importance as contributing to the first food of ( '<>r<';i<>nns
clupeiformis (Forbes '83a), of Labidesthes sicculus*, and
probably of other lake fishes.

*See Forbes "On the Food Relations of Fresh-water Fishes: a Summary and Dis-
cussion." Bull. 111. State Lab. Nat. Hist., Vol. II., Art. VIII.. ]>. 532. 1885.

238 Illinois State Laboratory of Natural History.

Since there are only two species of Limnocalanus known,
the key is naturally very simple, and only the most striking
differences arc used.

KEY TO THE SPECIES OF LIMNOCALANUS.

Based on the Characters of the Female.

1 (2). Hook-like process at inner apical angle of second

segment of outer ramus of fifth leg armed for the entire
length of both margins with fine symmetrical teeth.
Outer apical angle of same segment armed with a
stout serrate spine. Second basal segment without
plumose seta at outer apical angle. macrurus.

2 (1). Hook-like process at inner apical angle of second

segment of outer ramus of fifth leg armed on the en-
tire inner margin with large teeth and on the outer
margin with a few line ones". Outer apical angle of
same segment without spine. Second basal segment
without plumose seta at outer apical angle.

sinensis.

Based on the Characters of the Male.

1 (2). Right outer ramus of fifth legs 3-segmented (third

segment indistinct). Hook-like process of second seg-
ment of this ramus simply and hut slightly curved ;
provided with hyaline plate. Inner rami alike.

macrurus.

2 (1). Right outer ramus of fifth legs clearly 2-segmented.

Hook-like process of second segment of this ramus
somewhat sinuously curved. Inner rami unlike.

sinensis.

Limnocalanus macrurus Sars.

Limnocalanus macrurus. Sars. '62, p. '22V>.
Limnocalanus macrurus, Forbes. ! 82a, p. 049.
Centropages grlmaldii, de Guerne, "SO. p. 276.

Limnocalanus macrurus, Nordqvist, *S8, p. 31. PI. I., Fig. 9-11; PJ.
II., Fig. 1-5; Pi. III.. Fig. 1-1.

-In de Guerue and Richard's "Revision," Fig. 5a in the description of Plate IV.
should be Fig. 15a.

North American Centropagida. 23!)

Limnocalanus macrurus, de Guerue et Richard, '89b. p. 77. PI. IV.,

Pig. 5, 11. 12.
Limnocalanus macrurus auctus, Forbes, '90, p. 6-18.
Limnocalanus macrurus, Marsh, *93. p. 201, PI. IV. Fig. 7.
Limnocalanus macrurus. Marsh, '95, p. 11, PI. IV., Fig. 1, 2; PI. V.,

Fig. 1-5.
Limnocalanus macrurus, Herrick and Turner, "95. p. 49, PI. I., Fig. 1-1.
Limnocalanus grimaldii, Sars, "97. p. 39, PI. IV., Fig. 1— IS.

Body slender. Thorax rather more than one fourth as
broad as long, and composed of six well-defined segments,
of which the first (constricted at about the middle and armed
at the front with two hook-like processes pointing forward
and downward) is the longest — about equal to the three suc-
ceeding segments taken together; third and fourth segments
subequal, together slightly longer than the second, which is
armed on the dorsal and lateral surfaces, near the distal end,
with a row of rather stout spines; fifth segment somewhat
longer than the last, which is not produced laterally, hut
armed on each side with a very small spine. Abdomen of
Innale composed of four segments, the first about a third
longer than either of the two succeeding segments, which are
subequal. Furcal rami about a fifth longer than the first
segment, and slightly shorter than the second and third seg-
ments taken together; sparsely provided on the dorsal sur-
face with short sharp spines, and on the inner margin with
spines and hairs; one plumose seta on the outer margin at
the beginning of the distal fifth; and four plumose apical
setae and a delicate smooth seta on the dorsal surface near
the inner apical angle. In the male the first and fourth
abdominal segments are subequal, each about a fourth longer
than the fifth, which is the shortest ; second and third seg-
ments subequal, each about twice as long as the fifth ; second,
third, and fourth segments armed like the second abdominal
segment of the female. Furcal rami proportioned about as
in the female and similarly armed.

Antenme 25-segmented ; right male antenna geniculate
between the lcSth and 19th segments. The armature of the
segments is as follows: 1 and 10 have a short seta and two
sense-hairs; 2, a short seta and three sense-hairs; 3, a short

240 Illinois State Laboratory of Natural History.

seta and a sense-hair; 4, a short seta and a short spine; 5
and 7, a long seta, a short one, and a sense-hair; 6, a short
stunted spine; 8, a short broad seta, a short curved spine,
and a sense-hair; 9, a long broad seta and a sense-hair;
11, a short broad seta and a sense-hair; 12, a sense-club, a
short curved spine, and a short broad seta; 18, a short broad
seta and a sense-club; 14, a long seta and a short broad
seta; 15, a sense-club and two short broad seta?; 16, a long
seta, a sense-club, and a short broad seta; 17, a sense-club,
and abroad, pointed, knife-like process; 18, along sense-
club, and a hyaline lamella armed with teeth and extending
almost the entire length of the segment; 19, 20, and 21
(ankylosed, the suture between 19 and 20 obscurely indi-
cated), a blunt digitiform process at the inner apical angle,
a seta, a blunt stunted spine slightly below the middle, and a
stunted spine and a knife-like process still lower down ; 22
and 23, (ankylosed, suture indistinct), two seta? and a sense-
hair; 24 two seta?; and 25 (very short), four seta' and a
sense-club.

First basal segment of right fifth leg of male subquadrate.
Second basal segment about as "wide as the first and about
twice as long, provided at the outer apical angle with an in-
conspicuous hyaline process. First segment of outer ramus
considerably narrower than the second basal segment, less
than twice as long as wide; armed at the outer apical angle
with a stout spine, serrate on the inner margin, and on the
inner margin below the middle with a hyaline process. Sec-
aond segment slightly narrower than the first ; produced at
the inner apical angle into a hook-like process, which i^
armed on the outer margin, near the base, with two sharp
slender spines, and provided on both margins with a hyaline
lamina having an appearance of transverse st nation. The
hook is fully three times as long as the segment itself.

Inner ramus of right iifth leg three-segmented, the first
segment irregular in form, about twice as long as wide;
armed on almost the entire outer ma ruin with a few tine
hairs, and at the beginning of the distal third with a slender
plumose seta. Second segment somewhat wider than the

North American Centropagidae. 241

first, and rather more than twice as long as wide ; armed on
the outer margin with a few hairs and a moderately stout
plumose seta. Third segment about as wide as the second,
with margins sulcate ; outer margin armed with two stout
plumose setae, the proximal third with a few fine hairs ; inner
margin and apex each armed with two stout plumose seta?.

First basal segment of left fifth leg subquadrate, having
near the inner apical angle a large tubercle bearing a few
rather long hairs. Second basal segment somewhat narrower
than the preceding and not twice as long as wide ; armed at
the outer apical angle with a prominent hyaline process.
First segment of outer ramus subquadrate, rather more than
twice as long as wide ; armed on the inner margin, at the be-
ginning of the distal third, with a small process provided with
hairs, and at the outer apical angle with a short blunt spine
and a long stout movable spine serrate on the inner. margin.
Second and third segments ankylosed, forming one very long
narrow segment, slightly narrower than the first and more
than twice as long ; provided for the greater part of the inner
margin with hairs, and armed on the outer margin with three
spines, the upper two similar to the larger one of the preced-
ing segment, the third sometimes serrate on both margins ;
provided at the inner apical angle with a narrow digitiform
process about half as long as the segment itself and serrate
on the outer margin.

Inner ramus of the left fifth leg very similar in every re-
spect to that of the right leg.

First basal segment of fifth leg of female of the ordinary
form. Second basal segment about as wide as the first and
barely twice as long as w r ide ; outer half of the distal margin
produced in the form of an irregularly triangular flap extend-
ing over the margin of the first segment of the outer ramus.
First segment of outer ramus quadrate, about twice as long
as wide ; armed at the outer apical angle with a stout spine
serrate on the inner margin. Second segment somewhat nar-
rower than the first and not quite twice as long as wide ;
armed with hairs on both margins and at the outer apical
angle with one short spine and a longer, stouter one serrate

242 Illinois State Laboratory of Natural History.

on the inner margins ; inner apical angle produced in the form
of a moderately curved hook armed on both margins with
spines or teeth. Third segment narrower than the second
and fully three times as long as wide ; hairy on the upper
part of both margins, and armed on the outer margin, at the
beginning of the distal third, with two spines, one stout and
serrate and the other short and smooth; outer apical angle
armed with three spines, two short and smooth, the other
long and serrate on the inner margin ; inner margin sulcate,
and armed with two stout plumose setae ; apex armed with
two setre, the inner seta plumose on both margins, the outer
plumose on the inner margin and provided on the outer with
a hyaline lamina.

Inner ramus of fifth leg of female three- segmented. First
segment hairy on the outer margin ; outer apical angle armed
with a moderately stout plumose seta. Second segment sub-
quadrate, more than twice as long as wide ; hairy on both
margins ; armed at the outer apical angle with a plumose seta.
Third segment somewhat longer and broader than the second ;
margins sulcate, both hairy at the upper part ; armed with six
stout plumose seta', two apical and two on each margin.

Length of female 2.2 — 2.6 mm.; that of male 2.05 — 2.4
mm.

The above description was prepared from specimen- of
]j. macrurus sent by Professor Sars to the Illinois State Labor-
atory of Natural History, and from specimens of L. grimaldii
kindly sent by him to me. Nothing further need be said about
L. macrurus, the type of the genus, except in regard to syn-
onymy and distribution.

The original description of the species appeared in the
" Forhandlinger i Yidenskabs-Selskabet i Christiana " (Sars
'02). De Guerne ('86) described it under the name of ( 'entro-
pages grimaldii ; Nordqvist, in "Die Cahmiden Finlands" ('88 ),
made this a synonym of L. macrurus; and de Guerne and
Richard, in their "Revision" ('89b), acknowledged the cor-
rectness of Nordqvist's view. Recently, however, Professor
Sars, in his "Pelagic Entomostraca of the Caspian Sea"
('97), re-established de Guerne's form as a new species of

North American Centropagidce. 243

Limnocalan us, L. grimaldii de Guerne. Except for a difference
in size and in the proportions of the segments of the fifth legs
of both sexes, which segments are somewhat less robust in
the fresh-water form than in the one from the Caspian Sea,
and but for a slight though noticeable difference in the lateral
aspect of the head, the two forms exactly correspond. It
does not seem to me that such slight differences warrant the
establishment of a new variety, much less of a new species.
With the exceptions just noted, the details of structure men-
tioned in the foregoing description are equally prominent in
both forms, as are those noted in the following discussion of
the published figures of the species.

The best illustrations of L. mqcrurus are given in "Die
Calaniden Finlands " (Nordqvist, '88) and in the "Revision
des Calanides d'eau douce" (de Guerne et Richard, '89b),
although in neither publication are they strictly correct. 1 )e
Guerne and Richard's figures of the fifth pair of legs of the
female do not show the projection of the second basal seg-
ment over the first segment of the outer ramus, nor the hairs
on the inner margin of the second segment of this ramus and
on the third segment of the inner ramus, nor the serrations on
the spine at the outer apical angle of the last segment of the
outer ramus. Nordqvist says that the outer ramus has three
segments but figures it with two. The inner ramus he repre-
sents as smooth on the outer margin of all its segments, and
gives the ordinary form to the outer of the two setae on the
apex of the last segment of the outer ramus, while de Guerne
and Richard picture it with a hyaline lamina on both margins
and a few fine spinules on the inner margin. Neither is cor-
rect with regard to this seta, since it is plumose on the inner
margin and has a hyaline lamina on the outer one.

Both de Guerne and Richard's and Nordqvist's figures of
the fifth pair of legs of the male fail to show the hairs on the
inner margins of the inner rami, the hyaline processes on the
outer margin of the second basal segment of the left leg and
on the first segment of the right outer ramus, and the serra-
tions on the hook of the last segment of the left outer ramus.
Further, Nordqvist fails to figure the hyaline process on the

244 Illinois State Laboratory of Natural History.

second basal segment of the right leg, the two spines on the
outer margin near the base of the hook of the second seg-
ment of the right outer ramus, the serrations of the apical
spine of the second segment of the left outer ramus, and the
process on the inner margin of the first segment of the same
ramus. De Guerne and Richard omit the tubercle on the
inner apical angle of the first basal segment of the left leg,
the hairs on the inner margin of the second segment of the
left outer ramus, and the hyaline lamina on the process of
the second segment of the right outer ramus, which is figured
by Nordqvist as being on the outer margin only, while it is
really on both. Nordqvist also fails to show the spines at the
base of the outer margin of this hook.

I have had no opportunity to examine specimens of the
marine genus Centropages, but the drawings of the fifth pair
of legs of the female of L. macrurus and of C, hamatus are
so similar that it is hardly to be wondered at that de Guerne
regarded the two forms as belonging to the same genus. The
fifth pair of the legs of the males also show the same general
structure in the two genera, although they differ materially
in detail.

L. macrurus is the only species of the family Centropagida
which is common to Europe and America. This is probably
due to the fact that it occurs in both fresh and salt water,
and thus the Atlantic offers no barrier to its distribution. It
has been recorded from Sweden, Norway, and Finland, from
the Kara and Baltic Seas and the Gulf of Finland, and from
the ocean off Spitzbergen ; and it is probably widely distributed
in the countries of northern Europe and Asia. In America it
was first recorded from Lake Michigan (Forbes, '82), and
later, under the name of L. macrurus auctus, from Lake
Superior (Forbes, '90). Marsh ('93 and '95) found it in
Green Lake, Wisconsin, in Lake St. Clair, Michigan, and in
Lake Huron.

North American Centropagidce. 245

Limnocalanus sinensis Poppe.

Limnocalanus sinensis, de Guerne et Richard, 89b, p. 79, PI. IV.,

Fig. 4, 15, 15a, 16.
Linmocalwius sinensis. Herriek and Turner, '95, p. JO.

Body six- segmented, slender, more attenuate at the an-
terior than at the posterior part ; suture between' head and
thorax distinct. Second thoracic segment about as long as the
other five, which differ but little in length. Last two thoracic
segments distinct, the last segment somewhat produced pos-
teriorly and armed on each side with a short blunt spine.
First abdominal segment barely three times as long as the
second, which is but slightly longer than the fourth ; third
segment about one and three fourths times as long as the
second. Furcal rami more than twice as long as the third seg-
ment and barely four times as long as broad; somewhat
sparsely hairy within. All of the furcal seta? in both sexes dis-
tinctly plumose, the innermost seta much more slender than
the others and placed on the dorsal surface of the ramus, almost
directly opposite the base of the outer one. In the male the
first and fifth segments are subequal, each slightly longer
than the second and third, which are also about equal.
Fourth segment the shortest, about three fourths as long as
the second. Furcal rami fully three times as long as the
fourth segment, about four and a half times as long as
broad, and armed as in the female.

Antenna; 25-segmented, hardly extending to the base of
the furca. Plight antenna of the male moderately swollen
from the 12th to the 18th segments inclusive. The armature
of the segments anterior to the 10th segment is as follows:
1 1 has a sense-club and a short seta ; 12, a sense-club, a short
seta, and a short curved spine; 13, a sense-hair and a sense-
club; 14, a sense-hair, a sense-club, and a long plumose
seta; 15, a sense-hair, a sense-club, and along spine; 1(5, a
sense-hair, a sense-club, and a long plumose seta; 17 a
broad knife-like process and a sense-club; 18, a short
stunted spine, another spine somewhat longer, and a hya-
line lamina armed with teeth about half as long as the lamina
is broad ; 19, 20, and 21 (completely ankylosed), a short

246 Illinois State Laboratory of Natural History.

•stunted spine, a long plumose seta, two processes, and a
hyaline lamina armed with teeth about as long as the lamina
is wide and occupying about a third of the margin slightly
below the middle ; 22 and 23 (completely ankylosed), a short
seta, a short stunted spine, and a long plumose seta ; 24, two
long plumose setre ; and 25 (very short), three long plumose
seta- and a sense-club.

First basal segment of right fifth leg of male not characteris-
tic. Second basal segment irregular in form, about two and a
half times as long as wide, armed on the anterior aspect, below
the inner proximal angle, with a stout sharp spine, and at the
middle of the inner margin with a number of exceedingly short
hairs or spines. First segment of outer ramus narrower than
second basal segment, about one and three fourths times as
long as wide ; armed at the outer distal angle with a straight
sharp spine serrate on the inner margin. Second segment
produced in the form of a long stout sub-sigmoid hook, wid-
est some distance below the base and tapering gradually to a
rather blunt point ; inner margin of broadest part roughened
by a number of irregularly disposed ridges, otherwise both
margins perfectly smooth.

Inner ramus of right fifth leg three-segmented, the first
segment subelliptical, more than twice as long as wide, and
hairy at the middle of the inner margin. Second segment
considerably broader than the first, bulging out at the middle
and armed here with a few rather long hairs ; inner apical
angle armed with a rather short plumose seta. Third segment
subelliptical, more than twice as long as wide ; armed with six
stout plumose setre, two apical and two on each of the
lateral margins.

First basal segment of left fifth leg not characteristic.
Second basal segment about one and three fourths times as
long as wide ; armed at the outer distal angle with a plumose
seta, and at the middle of the inner margin with a few very
short hairs or spines; produced at the inner apical and
proximal angles into smooth hemispherical processes, the
lower of which is the larger. First segment of outer ramus
subquadrate, about twice as long as wide, produced at the

North, American Centropagidce. 247

middle of the inner margin into a smooth rounded process,
and armed at the outer apical angle with a stout straight
spine serrate on the inner margin. Third segment ahout
twice as long as its greatest width, dilated at the middle of
the inner margin and armed here with a few rather long
hairs ; outer margin armed with three spines similar to the
one on the preceding segment, and at the apex with a long,
narrow, slightly curved process, perfectly smooth, and some-
what longer than the segment from which it springs.

Inner ramus of left fifth leg three-segmented. First seg-
ment subquadrate, slightly more than twice as long as wide ;
provided at the middle of the inner margin with a hemispher-
ical process armed with a few scattered hairs. Second seg-
ment somewhat broader than the first and about as long ;
armed at the inner proximal angle with a small sharp spine,
and at the middle of the inner margin with two irregularly
roughened processes provided with hairs ; a long plumose seta
on the inner margin just below the lower of the two processes.
Third segment slightly narrower and shorter than the second,
both margins sulcate, armed with six stout plumose setae
arranged about as in the corresponding segment of the inner
ramus of the right leg.

First basal segment of fifth leg of female subquadrate.
Second basal segment about as wide as the first and approxi-
mately one and three fourths times as long as broad ; hairy
at the middle of the inner margin and armed on the outer
apical angle with a plumose seta. First segment of outer
ramus subquadrate, about one and three fourths times as long
as broad ; armed on the inner margin, near the proximal
angle, with a smooth hemispherical process, and on the outer
apical angle with a stout spine, serrate on the inner margin.
Second segment slightly narrower at the base than the first,
but widening distally and produced at the inner apical angle
into a stout hook-like process armed on the inner margin
with six or seven strong teeth, largest near the middle of the
hook, and near the proximal end with five or six smaller teeth.
On the outer margin of the hook and opposite the smaller
teeth of the inner margin are a number of rather minute

248 Illinois State Laboratory of Natural History.

teeth. Third segment about half as wide as the second and
approximately three times as long as its greater width ; inner
margin silicate and armed with live stout parallel plumose
setae; outer margin armed with two strong straight spines,
the upper at about the beginning of the distal third, the lower
at the apical angle, and both serrate on the inner margin.
Just within the apical spine are a short blunt process and a
long, narrow, awl-like process almost twice as long as the
segment.

Inner ramus of fifth leg of female three-segmented, the first
segment subelliptical, somewhat less than twice as long as
wide, and hairy at the middle of the inner margin. Second
segment a little wider than the first, about twice as long as
wide, hairy at the middle of the inner margin; outer apical
angle armed with a stout plumose seta. Third segment about
as wide as the first, margins sulcate ; armed with six stout
plumose seta?, two apical and two on each side.

Length of female about 1.65 mm. ; that of the male
1.60 mm.*

The above description is based on specimens kindly sent
me by Herr S. A. Poppe. On examination I found a few
minor differences between the specimens sent me and the
original figures. These differences I note below. The second
thoracic segment instead of being only as long as the two
succeeding ones is about as long as the remainder of the
thorax. The innermost f ureal, seta is plumose instead of
smooth — as figured in the original drawings. In the fifth pair
of legs of the male the spines on the outer ramus of the left
leg were found to be serrate on the inner margin instead of
smooth. The spine or seta on the outer apical angle of the
second basal segment of this leg is plumose. The inner
margin of this segment is hairy or minutely spinose. Neither
the short hook-like spine at the inner proximal angle of the
second segment of the left inner ramus, nor the stout straight
spine (serrate on the inner margin) at the outer apical angle
of the right outer ramus is figured or described in de Guerne
and Richard's "Revision." I was unable to find the hairs

* Measurements as given in de Guerne and Richard's" Revision " (89b).

North American Ceniropagidce. 249

which Poppe figures on the inner margin of the second seg-
ment, and on the outer margin of the third segment, of the
outer ramus of the fifth leg of the female.

This species differs so much from L. macrurus, that it
might almost be regarded as the type of a new genus, but
Poppe has not considered the differences as of generic value,
nor have de Guerne and Richard. Unlike L. macrurus, the
inner rami of the fifth pair of legs of the male although both
three-segmented differ from one another, and the right outer
ramus is composed of two segments instead of three. In the
female the differences are not so striking, for while the outer
rami are noticeably unlike, the inner rami are very similar.

This species was found in Lake Sitai, China, and in the
Whangpoo River, which flows from it, the waters of both of
which are perfectly fresh. To my knowledge it has not yet
been recorded from any other locality.

Epischura Forbes.

Scopiphora ( ?), Pickering, "44, p. 62.
Epischura, Forbes, *82a. p. 647.
Epischura, Herrk-k, '83a. p. 384.
Epischura, Ilerrick, '87, p. 13.
Epischura, Herrkk and Turner, '85. p. 81.
Epischura, de Guerne et RiehanV89b, p. 141.

Cephalothorax more or less distinctly six- segmented. Ab-
domen (furca included) composed of five segments in the fe-
male and of six in the male ; in the female, of the ordinary form
(nevadensis, nordenskibldi) or flexed to the right and provided
with a process on the right side of the second segment (hiaix-
tris) ; in the male, straight or very slightly flexed (nordenski-
oldi) or strongly flexed to the right (lacustris, nevadensis) ; in
the males of all species, second, third, and fifth segments pro-
vided on the right side with processes. Furcal rami hairy
on the inner margin, provided in both sexes with three plu-
mose terminal setae, one slender simple seta at the inner
apical angle, and a stout spine at the outer apical angle.

First pair of antennae 25-segmented. Right male antenna
geniculate between the 18th and 19th segments; segments

250 Illinois State Laboratory of Natural History.

19 — 21, and 22 and 23 ankylosed ; antepenultimate segment
unarmed ; segments preceding geniculation very slightly
swollen. Second pair of antenna! about as in Diaptomus.

All the swimming legs biramose, the outer ramus three-
segmented, the inner, one-segmented. Fifth pair of legs of
the female alike, uniramose, three-segmented, the first seg-
ment of the ramus being, however, really the second basal
segment ; armed at the outer apical angle with a hair or deli-
cate spine. Third segment armed with a varying number of
spines (5 — 7).

Fifth pair of legs of the male unlike, uniramose, modified
into a grasping organ. Eight leg two- (lacustris, nevadensis)
or three-segmented (nordenskioldi); last segment almost
always flexed. Left leg three-segmented, the first segment
produced on the inner margin to form a strong hook-like
process ; last segment variously armed on the outer margin
with a number of spines, and provided on the inner margin
with fine long hairs.

Female generally bears spermatophore, and does not carry

eggs m egg- sac.

Inhabits* deep fresh water lakes.

As will be seen from the above, the doubtful E. fiuviatilis
Herrick has not been considered in this description, but only
the three recognized species, lacustris, nevadensis, and norden-
skioldi.

The species of this genus seem not to be fully differentiated
from each other. This is illustrated by the variable armature
of the fifth pair of legs of the females, nevadensis having
sometimes one and sometimes two spines at the outer apical
angle of the second segment and either six or seven spines on
the last segment, and nordenskioldi also varying in the latter
respect, having sometimes five and sometimes six spines.
All female specimens of lacustris observed, were constant in
the armature of the fifth legs, but in the left fifth leg of the
male the second segment, although generally unarmed, was
sometimes provided at the outer apical angle with a small
spine.

This genus, confined so far as known to North America,

North American Centropagidce. 251

and represented in different sections by different species, is
found from Newfoundland on the north and east to Wash-
ington on the west, and as far south as central Illinois and
Indiana.

KEY TO THE SPECIES OF EPISCHUBA.

Based on the Characters of the Female.

1 (2). Abdomen flexed to the right ; second segment armed

on the right side with a process. Furcal setae and
spines very broad. Fifth leg with last segment twice
as long as the first ; last segment armed with seven
spines. lacustris.

2 (1). Abdomen straight; second segment unarmed. Fur-

cal seta? and spines of ordinary width.

3 (4). Fifth legs very robust, first segment almost as wide

as long ; second segment sometimes armed with two
spines; third segment armed with six (occasionally
seven) spines. nevadensis.

4 (3). Fifth legs slender, first segment considerably longer

than wide ; second segment armed with a single small
spine ; third segment armed with five (sometimes six)
spines. nordenskioldi.

Based, on the Characters of the Male.

1 (2). Abdomen straight, abdominal processes small and

inconspicuous. Eight leg three-segmented, the first
segment armed on the inner margin with a hook ; sec-
ond and third segments armed at the outer apical angle
with a small spine. Process on first segment of left
leg but slightly curved. nordenskioldi.

2 (1). Abdomen flexed to the right; abdominal processes

large. Eight leg two-segmented.

3 (4). First segment of right leg with subtriangular toothed

plate on the inner margin, and a hair at the outer
apical angle. First segment of left leg very stout and
strongly curved ; second segment unarmed.

nevadensis.

252 Illinois State Laboratory of Natural History.

4 (3). First segment of right leg entirely unarmed. First
segment of left leg with comparatively slender process ;
second segment armed at the outer apical angle with a
small spine. lacustris.

Epischura nordenskioldi Lilljeborg.

Epischura nordenskioldi, de Guerne et Richard. 'e9b, p. 04, PI. I.

Fig. 36; Pi. II., Fig. If), 23.
Epischura nordenskioldi, Herrick and Turner, '95, p. 85, Pi. XI.. Fig.

2, 5, 9.
Epischura nordenskioldi. Schrneil. '9S. p. 183.

About medium size, body rather robust, widest in front of
middle. Cephalothorax six-segmented, the first two segments
confluent and together somewhat longer than the remainder;
third segment slightly longer than either of the last three,
which are subequal ; last two segments distinct, the last
segment produced on each side at the posterior angle into
a bluntly-rounded lobe armed at the tip with a minute
spine. Abdomen (including furca) five-segmented, slender.
a little less than half as long as the cephalothorax ; first two
segments indistinctly confluent below ; third segment slightly
longer than the fourth. Furcal rami about twice as long as
broad and ciliate on the inner margin ; armed at the apex
with three slender plumose setae fully three times as long as
the ramus itself, at the outer apical angle with a short stout
spine, and on the dorsal surface, near the inner margin, with
a delicate smooth seta. Abdomen of male (furca included)
six-segmented, the second, third, and fifth segments armed on
the right side with prehensile processes ; flexed to the right but
slightly or not at all. First segment somewhat broader than
long, slightly produced along the left margin into a process
ending at the posterior angle in a lobe-like expansion. Sec-
ond segment slightly narrower and longer than the first ; pro-
duced on the right side in the form of a subtriangular plate,
somewhat longer than w 7 ide and pointing obliquely backward.
The process is armed at the tip with a small sharp spine,
on the inner margin, near the apex, with two or three rather
large teeth, and within these with a number of smaller

North American Centropagidce. 253

ones. Third segment slightly shorter than the preceding;
process very simple, small and inconspicuous, bluntly pointed,
extending almost straight backward ; armed on outer margin,
near the tip, with a slight, blunt protuberance. Fourth seg-
ment unarmed, about half the length of the first. Fifth
segment about as long as the fourth ; armed with a narrow
triangular plate, broadest anteriorly and bluntly rounded at
the apex. Dextral margins of the fourth and fifth segments
tuberculate. Furcal rami about as in the female.

Antenna? 25-segmented, extending almost to the base of the
furca. Eight antenna of the male geniculate between the
18th and 19th segments ; segments preceding the geniculation
slightly or not at all swollen.

Eight fifth leg of the male three-segmented. First seg-
ment irregular in form, about twice as long as wide, armed
on the outer margin, near the distal angle, with the usual deli-
cate hair ; inner margin provided with a curious, smooth,
bluntly-pointed hook-like process extending downward almost
parallel to the margin. Second segment irregular, about
twice as long as wide ; outer margin smoothly convex, armed
near the distal angle with a small spine ; outline of inner
margin sinuous. Third segment long and narrow, with a
broad basal portion about half as wide as the segment is long ;
curved inward slightly at the tip and armed here, on the outer
margin, with a minute spine.

First segment of left fifth leg with a subquadrate main por-
tion produced on the inner margin into a long, smooth broad
hook but slightly curved ; armed at the outer distal angle
with the usual hair. Second segment somewhat narrower
than the first, subquadrate, about twice as long as wide ; outer
distal angle armed with a small sharp spine; inner margin
sometimes with indications of minute teeth or serrations at
about the middle. Third segment curved inward slightly,
about as broad as the second and fully four times as long as
broad ; armed on the outer margin with four rather small
sharp spines, the first at about the middle, the second midway
between this and the apex of the segment, the other two near
the apex and nearer together than the upper ones ; armed on

254 Illinois State Laboratory of Natural History.

the distal part of the inner margin with long delicate hairs.
This segment is much simpler than the corresponding seg-
ment of lacustris and nevadensis.

Fifth pair of legs of the female imiramose, three-segmented.
First segment subquadrate, somewhat longer than wide,
armed near the outer distal angle with a hair or delicate
spine. Second segment somewhat narrower than the first
and slightly longer ; armed at the outer apical angle with a
small sharp spine. Third segment slightly narrower than
the second and barely one and a half times as long ; armed
with five or six spines*, two (one) outer, one inner, and three
apical. Of the outer spines, the upper one is at about the mid-
dle of the segment and the lower one is directly opposite the
inner spine. Of the apical spines, the middle one is spinu-
lose on both margins and the outer one on the inner margin. +

Length of female 1.9 mm. ;t that of male 1.1 mm.

The above description was prepared from specimens kindly
sent me by Dr. Lillejeborg, the measurements, however, with
the modification explained in the foot-note, being those given
in the original description. The material was a part of that
collected by Dr. C Xystrom, a member of the Xordenskiold
expedition to Greenland in 1871, and was not in the best
state of preservation, owing no doubt to the length of time
since its collection.

Figures of this species may be found in de Guerne and
Richard's "Revision" ('89b), and imperfect copies of these
in Herrick's "Synopsis" (Herrick and Turner '95). The
fifth pair of legs of the male are correctly represented in the
"lievision" except that the spine at the outer apical angle of
the right leg is not shown ; indeed it is not mentioned in the
description. The spine figured on the outer margin of the

* The armature of this --eminent differs somewhat in different specimens. See on
a subsequent page the discussion in regard to the fifth leg of the female.

t Having only a few specimens to study. I could not satisfactorily determine
whether the other spines were also spinulose or not. but I am quite positive with re-
gard to the two mentioned. I think it likely that they are armed as in lacustris.

i It is quite evident that a mistake was made in regard to the measurements given
in the original description: " Length of female, caudal seta' excepted, about 3.9 mm.,
and of male 1.1 mm." In the specimens I examined there was no such difference in
length in favor of the female; in fact the single entire female I had the opportunity
to measure was 1.333 mm. in length, while the average length of five males was con-
siderably above this— 1.698 mm. I have hesitated to substitute these measurements
because of the limited number examined, and have altered Lillejeborg's figures to
what I think they were intended to he.

North American Centropagidce. 255

•

second segment of the right leg, which Schmeil ('98) says he
could not find, was present in all the specimens examined by
the writer. In one of the two specimens of females examined
the last segment of the fifth leg was armed with five spines,
as shown in the original figures, while the other had six.
I think that six may perhaps be found to be the rule, in
which case the species approaches nevadensis and laeustris
more closely, the former having six and sometimes seven
spines, and the latter constantly seven. The fact that none
of the other writers, Lilljeborg, de Guerne and Richard, and
Schmeil, have mentioned the existence of a sixth spine would,
however, militate against this assumption.

The male of nordenskioldi is very easily distinguished from
the males of the other two species. The fifth pair of legs,
while of the same general type as in the rest of the genus, are
less modified and yet very characteristic. But for the fact
that it is, as a rule, difficult to make out, the hook-like process
on the first segment of the right leg would alone serve to
distinguish nordenskioldi. Further, the right leg is three-
segmented instead of two ; the last segment is armed on the
outer margin, at the apex, with a small spine ; and the hook
on the first segment of the left leg is comparatively simple.'
The abdomen is also less modified than that of nevadensis
and laeustris. Instead of being quite strongly flexed to the
right it is almost or entirely straight, while the processes are
small and inconspicuous, there being some difficulty in dis-
cerning the one on the fifth segment.

The fifth pair of legs of the female also serve, though not
so readily, to distinguish this species. They differ from those
of laeustris in that the last segment is armed with only five or
six spines, instead of seven, and in the relative length of the
segments. From the fifth legs of nevadensis they may be
distinguished by the difference in proportions, those of neva-
densis being much more robust than those of nordenskioldi,
which are intermediate between the other two. The different
arrangement of the spines on the last segment, the occasional
absence of the sixth spine on this segment, and the presence,
at least occasionally, of a second spine at the outer apical

256 Illinois State Laboratory of Natural History.

angle of the second segment of the leg of nevadensis, will all
assist in determining the species.

De Guerne and Richard (89b) make the statement that tin-
females always have the spermatophore — which they describe
as curved in a semicircle around the abdomen — attached. ( hi
none of the females examined by the writer was this structure
present. It may of course have been torn off, although
even then the statement that it is always present seems to
me too strong, since in E. lacustris and E. nevadensis the
female, even when mature, is very often found without a
spermatophore.

Epischura nevadensis Lilljeborg.

Epischura nevadensis , de Guerne et Richard, "89b, p. 93. PI. II., Fig.

17.24; PJ. III., Fig. 21.
Epischura nevadensis columbice, Forbes/93. p. 254. PI. XLL, Fig. 19-21.
Epischura nevadensis, Herrick and Turner, '95. p. 84. PI. XL, Fig.

1, 6, 8.
Epischura nevadensis columbice, Herrick and Turner. '95, p. 84. PJ.

XL, Fig. 4, 10.
Epischura nevadensis, Schmeil, '97, p. 183.

Of medium size and somewhat oval in form, broadest
before the middle. Front armed on each side with a hook-
like process pointing downward. Cephalothorax six-seg-
mented, the second segment the longest, about twice as long
as the first or last, which are subequal, the remaining three
segments subequal, each about a fourth the length of the
second. First two segments somewhat confluent, as are the
last two; last segment, seen from above, not produced and
entirely unarmed. Abdomen (furca included) composed of
five segments, the first two confluent and together almost as
long as the two following, which are subequal and slightly
longer than the furca. Furcal rami subquadrate, very short
and broad, and provided on the posterior part of the inner
margin with a few fine hairs ; armed at the outer apical angle
with a stout pointed spine, and at the inner apical angle with
a slender smooth seta, posterior margin armed with three long
delicately plumose setae, of which the inner is the longest,
the other two being about equal. In the male the abdo-

North American < 'entrap a g idee. 257

men is asymmetrical, flexed to the right, and consists of six
segments (furca included). The segments vary but little
in length, the furca being, however, the shortest, the fifth,
second, and first increasing in length in the order of their
mention, the third and fourth subequal, each slightly longer
than the first. Seen from above, the first segment is pro-
duced slightly to the left at its posterior margin. Second,
third, and fifth segments armed with processes on the right
side. The process on the second segment is a broad thin
lamina about as long as the segment is broad, smooth on the
convex anterior margin and for about the distal fourth of its
posterior margin (which is almost straight), but for the re-
maining three fourths of this margin provided with minute
irregular teeth having a tendency to point toward the abdo-
men ; apex acute and slightly recurved. The process on the
third segment springs from the posterior part as a broadly
rounded smooth hyaline lamina slightly longer than broad.
Fourth segment unarmed. Fifth segment provided with two
processes, the anterior one (pointing forward and upward)
consisting of a narrow irregularly triangular plate with an
acute apex and smooth margins, the posterior one having the
form of a truncated triangle, armed at the apical margin with
three or four large equal teeth and one or two much smaller
ones. Posterior to this process the right margin of the seg-
ment is armed with a row of bead-like tubercles which, near
the suture between the furca and this segment, lengthen to
form two or three blunt spines. Furcal rami slightly longer
proportionally than in the female, but similar in other respects.

Antenna; 25 - segmented, long and slender, extending
slightly beyond the posterior end of the third abdominal seg-
ment in the female and beyond the fourth segment in the
male. Right male antenna geniculate between the 18th and
19th segments; segments 19, 20 and 21, and 22 and 23
ankylosed ; antepenultimate article unarmed.

Right fifth leg of male two-segmented. First segment
irregularly pentagonal, the longest base forming the outer
margin, which is armed near the distal angle with a delicate
seta; basal half of inner margin armed with a broad irregu-

258 Illinois State Laboratory of Natural History.

lar hyaline plate which near its middle is somewhat produced
and provided with a number of delicate serrations. Second
segment consists of a broader basal portion and a narrow
terminal part, the latter constituting about three fourths the
entire length, and extending upward to the middle of the
inner margin of the preceding segment ; apex produced at
the inner margin, forming a kind of hook.

Left fifth leg uniramose, three-segmented. First segment
armed near the outer apical angle with a delicate seta and
produced on the inner margin into a large plate-like hook
almost as broad as the segment and strongly curved inward.
Second segment irregular in shape, slightly longer than broad,
and unarmed.* Third segment or terminal hook contorted,
about twice as long as the second segment; basal portion
broad, with a projecting inner angle ; inner margin sinuous,
the lower curve densely provided with fine long hairs ; outer
margin armed with three short, sharp unequal spines increas-
ing in size from above downwards ; the attenuate apex pro-
vided with a spine considerably larger than the others.

Fifth leg of female uniramose, three-segmented. First
segment subquadrate, with flaring sides; armed near the
outer apical angle with a rather delicate smooth seta. Sec-
ond segment subquadrate, about one and a half times as long
as the first and about two and a half times as long as broad ;
armed at the outer distal angle with a short sharp spine
(occasionally with two subequal spines). Third segment
(terminal spines excluded) about as long and wide as the
second ; outer margin armed with a short sharp spine at
about the beginning of the distal half (another spine occa-
sionally present a short distance above this); apex provided
with three spines, the two outer ones subequal and the mid-
dle one considerably larger ; inner margin armed with two
spines near the apex of the segment, the upper about half
the size of the lower, and the margins of both denticulate.

Length of female 2-2.5 mm.; that of male 1.7-2.1 mm.

The above description is based on type specimens of E.

i mi one or two specimens I noticed <i u >te a larsje tubercle, with a roughened up,
projecting from the anterior aspectof tins segment near the outer proximal ai

Out did not ti nt 1 it at all constant.

North American Centropagidce. 259

nevadensis Columbia Forbes; on other specimens collected in
the same localities — Swan Lake and Flathead Lake, Montana ;
and on specimens from Gamble's Lake and Lake Pend
d'Oreille, Idaho, from Lake Tahkemitch and Tsiltcoos Lake,
Oregon, and from Lake Union and Lake Washington, Wash-
ington, sent to the State Laboratory by Messrs. Evermann
and Meek of the U. S. Fish Commission. I had also a large
number of the Nevada form kindly sent me by Prof. Lillje-
borg, but, unfortunately, there was not a single mature indi-
vidual in this lot, and for this reason I cannot say on my own
responsibility that E. nevadensis Lilljeborg and E. nevaden-
sis Columbia Forbes are identical. A careful examination of
the material at hand, however, inclined me to that belief, and,
moreover, Professor Schmeil, both in a personal letter and
later in the "Bibliotheka Zoologica " (Schmeil, '97) says that
they are, after having examined authentic specimens from
both localities. He states also that Professor Forbes was
perfectly justified in establishing his Columbia, as a new
variety, since Lilljeborg's descriptions and figures are inac-
curate in several respects. In the following paragraph are
given the points in which my observations differ from those
of Forbes and of Lilljeborg.

In all the specimens examined the segments of the fifth leg
of the female are proportionately longer and narrower than
figured by Lilljeborg. This fact may be due to his having
.made his drawings from an individual not perfectly matured.
This difference was noted by Forbes in his description of
Columbia ('93). The appendage near the outer distal angle
of the first segment of this leg is correctly drawn as a seta by
Lilljeborg, while Forbes's figure represents it as spine-like.
The fact that a second spine is occasionally found at the outer
distal angle of the second segment must have been observed
by Lilljeborg, since his drawings show it, although no mention
of it is made in the original description of nevadensis (de
Guerne et Richard, '89b). Forbes refers to it in his descrip-
tion of Columbia? but does not figure it. A seventh spine on
the outer margin of the last segment was correctly said by
Forbes to be occasionally present. Lilljeborg does not seem

260 Illinois State Laboratory of Natural History.

to have found this spine, but Schmeil confirms Forbes's state-
ment. The inner two spines on the last segment are serrate
on both margins, but this fact is shown in none of the figures,
nor is it mentioned in the literature referred to. The first
segments of the fifth pair of legs in the male are each provided
with a rather delicate seta near the outer distal angle. This
is shown in the published figures, but Lilljeborg mentioned
only the one on the left leg. The ordinary appearance of the
lamina of the second segment of the right leg is best shown in
Forbes's figures.

This species is quite common in the western United States,
having been found to occur in considerable quantities in col-
lections from Nevada, Idaho, Oregon, Washington, and Mon-
tana, and further collections will no doubt show a still more
general distribution. It occurred in collections with Diap-
tomus ashlandi Marsh and with I), minutus Lilljeborg.

Epischura lacustris Fokbes.

Scopiphora vagans (?), Pickering. *4-l, p. 62.

Epischura lacustris. Forbes, '82a, p. 648, PI. VIII., Fig. 15, 16, 21-23.

25-27; P). IX., Fig. 8.
Epischura lacustris, Herrick, '84, p. 131, PI. Q, Fig. 15.
Epischura lacustris, de Guerne et Richard, "89b, p. 90, PJ. IV.. Fig.

3, 9, 10.
Epischura lacustris, Forbes, '90, p. 704, PL I., Fig. 1-5; PI. II., Fig. 7.
Ejrischura lacustris. Forbes, '93, p. 255.
Epischura lacustris, Marsh, "93, p. 200, PI. IV., Fig. 6.
Epischura lacustris, Marsh, '95. p. 10, PI. II., Fig. 1-6; PI. III., Fig

1-6.
Epischura lacustris, Herrick and Turner, '95, p. 82. PI. XIII., Fig.

15.

Of medium size. Body elliptical, widest before the middle.
Cephalothorax composed of six segments, the first two sub-
equal and together somewhat longer than the remaining four.
Third, fourth, and fifth segments subequal and together about
equal to the first. Sixth segment slightly longer than any of
the three preceding ; not produced laterally. Abdomen flexed
to the right, the first segment very short. Second segment the
longest and about equal to the remainder of the abdomen

North American Centropagidce. 261

(furca included) ; produced on the right side into a slight
semicircular process. Third segment and furcal rami sub-
equal, each slightly longer than the fourth segment. Furcal
rami very broad and delicately hairy within ; armed at the
outer apical angle with a short, sharp broad spine (the one
on the right ramus the larger), and within this with three
delicately plumose apical setpe, the outer of which, at the base
and for a considerable part of its length, is even broader than
the spine but gradually tapers and ends in a delicate flagellum,
while the other two sets are much narrower than the outer
seta but about as long. At the inner apical angle is a much
smaller delicate smooth seta. Abdomen of male much
more strongly flexed to the right than that of female, com-
posed of six segments (furca included), the second, third,
and fifth produced on the right side. First segment short,
about twice as broad as long. Second segment somewhat
longer than the first, the process about as long as the segment
is wide, with a smooth anterior margin and an irregularly
serrate inner margin with a hooked tip. Third segment about
as long as the first ; process about as long as the segment,
..of nearly the same width throughout, the tip bluntly rounded
and armed anteriorly with a hemispherical tuberculate
cushion or pad, and on the posterior margin, almost opposite,
with another similar process. Fourth segment slightly longer
than the third, and unarmed. Fifth segment slightly shorter
than the fourth and armed with two processes, the anterior
of which is perfectly smooth, pointing forward and to the
right, the posterior one pointing almost straight to the right,,
armed on the anterior margin with a number of large teeth
(8 — 10), its posterior margin smooth at the tip but minutely
denticulate for the basal three fourths. Furcal rami armed
about as in the female but with no such difference in the width
of the apical setae and with narrower spines.

Antennas 2 5 -segmented, extending to the posterior margin
of the fourth abdominal segment. Right male antenna slen-
der, geniculate between the 18th and 19th segments; seg-
ments 19 — 21, and 22 and 23 ankylosed ; antepenultimate
segment without special armature.

"2i)"2 Illinois State Laboratory of Natural History.

Left fifth leg of male uniramose, three-segmented. Firsl
s< gment subquadrate, produced on the inner margin into a
long, broad, strongly curved hook-like process about twice as
long as the main part of the segment and armed at the tip
with a broad blunt spine; provided at the outer apical angle
with a rather stout hair or spine. Second segment about as
long as the first but much narrower; margins parallel, the
inner margin concave ; usually unarmed but sometimes pro-
vided at the outer apical angle with a minute sharp spine.
Third segment irregularly triangular in form and about one
and a half times as long as the second, somewhat produced
at the inner proximal angle ; armed at the tip with a short
broad spine, on the outer margin with three spines, dividing
it approximately into thirds, and on the inner margin with a
close row of long delicate hairs.

Eight fifth leg uniramose, two-segmented. First segment
irregular in form, the outer margin almost straight, the inner
produced on the lower half into a large lamella or rlat
process* ; usual seta at the outer apical angle wanting. The
second segment consists of a broader basal and a narrower
terminal part which is always rlexed inward and upward;.*
inner margin slightly produced at the tip.

Fifth leg of female uniramose, three-segmented. First
segment barrel-shaped, armed at the outer apical angle with
a delicate spine. Second segment about half as wide as the
first and about three times as long as wide : armed at the
outer distal angle with a minute spine. Third segment
slightly narrower than the second and about one and a half
times as long; armed on the outer margin with three spine>
(the upper two smooth, the lower one spinulose) ; on the
apical margin with three spines (the outer two spinulose on
their opposed margins and the inner one on both), and on th-
inner margin with one spine, spinulose on the inner margin.

Length of female 1.784 mm. ; that of male 1.370 mm.

The above description was prepared from type specimens,
from Dr. Forbes's slides, from specimens taken in the same

*In one or twn specimens I thought I saw indications of several teeth, similar to
those in E. nevadensis, but could not fully satisfy myself of their presence.

North American Centropagidce. 263

Ideality as the type, — Normal, 111., — and from other speci-
mens collected at various times and places in Illinois, Indiana,
and Michigan.

This species, the type of the genus, was first described in
the "American Naturalist" (Forbes, '82a), and de Guerne
and Richard, Forbes, Herrick, and Marsh have since published
descriptions and figures. Scopiphora vagans Pickering is, as
de Guerne and Richard, Herrick, and Marsh have said,
probably identical with Epischura lacustris, but this can never
be definitely determined since the following quotation is all
that has been published concerning S. vagans.

"Genus Scopiphora, Pickering. Body small. Eye single,
in the anterior margin of the shield. Antenna; large, and as
long as in the preceding genus ^Cyclops], and has the same
motions in the water. Abdomen terminating in two styles
each with three setie; a brush under the last or last three
joints. Ovaries none. Legs spiny.

" S. vegans (Pickering) MSS."*

This is, of course, too meager a description upon which to
establish a genus, and the writers mentioned above, as well
as Dr. Schmeil ('98), have considered it insufficient and
allowed Forbes's name to stand. Herrick explains the "brush"
as some parasitic growth. May it not rather have been the
fifth, and perhaps the fourth, pair of legs projecting straight
backward under the abdomen which caused this appearance?

In the following three paragraphs are noted the points in
which my observations differ from those of previous writers
as shown by their descriptions and figures.

The abdomen of the male is very complicated in its seg-
mentation, and in the original description (Forties, '82a) was
described as having processes on the second, third, fourth,
and fifth segments. All figures published previous to the
appearance of " A Preliminary Report on the Aquatic In-
vertebrate Fauna of the Yellowstone National Park, etc."
(Forbes, '93), including those of de Guerne and Richard's
" Revision," were incorrect. In Forbes's paper attention was
called to the fact that the fourth segment was without a

* See Pickering, '44.

'2(')4 Illinois State Laboratory of Natural History.

process but that the fifth had two as in all the other species,
and in the same year Marsh in his " Cyclopidae and Calanidae
of Central Wisconsin" ('93), published the first correct figure
of the abdomen, but seems to have been unaware of it, since
in his "Cyclopidae and Calanidae of Lake St. Clair" ('95) he
says,'' Forbes has recently called attention to the fact that the
fourth abdominal segment of the male is without a process
and that the fifth bears two processes." His figure in this
paper also ('95) is correct.

The armature of the fifth leg of the female is nowhere
represented with exact correctness. The first segment is cor-
rectly figured by Forbes ('90) and by de Guerne and Richard
in their " Revision," with a spine at the outer apical angle, but
this is wanting in Marsh's figure ('95). The second segment
is correctly shown in all the illustrations. The third segment,
which has three outer spines, three apical ones, and one inner
spine, is represented in all the figures without the upper spine
on the outer margin. The armature of the spines themselves
is nowhere correctly shown, the differences being evident by
comparing the specific description with the drawings.

The left fifth leg of the male is usually represented with the
outer apical angle of the first segment unarmed ; de Guerne
and Richard, however, figure this correctly. The second seg-
ment is often armed with a spine at the outer apical angle,
but this is wanting in all of the figures ; nor are the three
spines on the outer margin of the third segment shown, there
being in most cases only one but sometimes two. The right
leg is correct in all the figures.

The spermatophore is very persistent, and a female is rarely
found without one or several. In this species it is a long tube-
like sac extending upward and to the left under the abdomen,
differing considerably from the same appendage in E. neva-
densis, in which it extends downward and backward, and
when in position has somewhat the appearance of a keel. It
is also much longer in E. lacustris than in E. nevadensis.

/•.'. lacustris is quite common in the North Central States,
being found in the deeper, clearer lakes in connection with
Limnocalanus macrurus Sars, Diaptomus sicilis Forbes, 1>.

North American Centropagidce. 265

ashlandi Marsh, D. pallidus Herrick, or D. siciloides, I), on
gonensis, and 1>. nlinutus, Lilljeborg, and sometimes with two
or more of these species. It has been found in Illinois,
Indiana, Ohio, Minnesota, Michigan, Wisconsin, and also at
East Portland, Oregon.

DOUBTFUL SPECIES.

Epischura fluviatilis Heerick.

Epischurafluviatilis, Herrick, '83a, p. 381. PI. V.. Fig. 10-20.
Epischura fluviatilis, Herrick, "84, p. 133. PI. Q, Fig. 14-16.
Epischurafluviatilis, Herrick, '87, p. 13, PI. II., Fig. 21-24.
Epischurafluviatilis, de Guerne et Richard, ? 89b, p. 92, PI. IV., Fig.

13. 20.
Epischurafluviatilis, Forbes. "93. p. 254 (foot-note).
Epischurafluviatilis,. Herrick and Turner, '95, p. 83, PI. XIII., Fig.

14-16.
Lamellipodia [Epischura] fluviatilis. Sehrneil, "98, p. 183.

Of small size, body rather slender ; color greenish- blue.
Cephalothorax imperfectly six-segmented. Abdomen three-
segmented, differing in no way from that of Diaptomus except
in the number of f ureal seta?. In the male the second abdom-
inal segment bears on its left side a peculiar process con-
sisting of two parts forming a clasping organ, the inner part
of which is about as long as the third segment and armed at
the apex with two small spines, the outer part being slender,
curved, and about twice as long as the inner.

Antennae 25-segmented, extending somewhat beyond the
end of the thorax. Eight male antenna geniculate between
the 18 and 19th segments; last six segments not ankylosed,
enlarged portion not greatly swollen.

Swimming legs biramose, the outer ramus consisting of
three segments, the inner ramus of one segment. Basal seg-
ments of the two legs fused beyond the last.

Fifth pair of legs of male uniramose, the two basal seg-
ments entirely fused. Eight fifth leg three-segmented, the
first two segments subquadrate and subequal, about three
times as long as wide and entirely unarmed. Third segment
slightly longer and broader than the second, tapering to a

266 Illinois State Laboratory or' Natural History.

blunt point and armed on the outer margin with three spines.

Left fifth leg very peculiar, consisting of a single lamelli-
form subcircular segment, armed on the flat surface with two
opposable claws forming a forcipate structure.

Fifth pair of legs of female uniramose, three-segmented
(two basal segments). First segment about twice as long as
broad. Second segment narrower than the preceding and
about twice as long ; armed at about the middle of the outer
margin with a spine. Third segment curved inward, some-
what longer and narrower than the second, ending in a sharp
point, and armed on the outer margin with two spines divid-
ing it approximately into thirds.

Mulberry Creek, Cullman county, Alabama.

Length, about 1.103 mm.

The above description was compiled .from drawings and
descriptions found in Herrick's writings (Herrick, '83a, '84,
and '87, and Herrick and Turner, '95), since all attempts to
obtain material from Cullman county, Ala., or from any
other part of that State, were unsuccessful.

A brief discussion of the published figures and descriptions
will not be superfluous in connection with' a doubtful species.
In the American Naturalist, Vol. 17 (Herrick, '83a), is pub-
lished the original description of E. fluviatilis, and a figure
representing apparently a ventral view of the last thoracic
segment and abdomen, and the fifth pair of legs of the male.
In this drawing the process on the third segment is on the
right side, making it sinistral in the animal as Herrick says
it is ; but in his " List of Fresh-water and Marine Crustacea
of Alabama" ('87) he gives another figure, which is just as
apparently a ventral view of the same thing. In ttris latter
figure, however, the process is sinistral, making it dextral in
the animal, and also making the left leg three-segmented
and the right leg one- segmented. Two other figures (Her-
rick, '84 and Herrick and Turner, '95) also show the process
on the right side, but there is nothing to indicate whether
they are dorsal or ventral views.

Now, in regard to the synonymy. If the process is on the
left side, as is maintained in all of Herrick's descriptions, this

North American Centropagitke. 267

species cannot belong to the genus Epischura, as has already
been pointed out by Forbes ('93, p. 254) and Schmeil ('98),
since the process cannot be homologized with the similar
process in Epischura proper. If, however, the process is
dextral, as shown in three out of the four figures published,
it might be more easily homologized with the process in the
other species of the genus. It would also be more likely that
the left leg was three-segmented and the right one especially
modified into a clasping organ if E.fluviatilis belonged to this
genus, although even then the fact that the second segment
of the left (right ?) leg is not at all produced inwardly and the
structure of the right (left ?) leg is radically different would
present difficulties. The fifth legs of the female are very
similar to those of Epischura, but partake slightly of the
characters of Heterocope. Schmeil says ('98) that, judging
from analogy with other genera, there is one basal segment
too many in the fifth pair of legs of both sexes. Herrick, in
the " American Naturalist" (Herrick, '83), gives a drawing of
a swimming leg of E.fluviatilis, with its one-segmented inner
ramus, which, if the upper, incomplete part shown is to be
regarded as another segment, certainly gives it, as Schmeil
says, one too many segments. If, however, it is an adhering
part of the thoracic segment, it will differ from a swimming
leg of E. lacustris only in that in lacustris the first basal seg-
ments instead of being fused their entire length, as in fluvia-
tilis, are fused for about the basal two fifths only. The fifth
legs of both sexes are similar in arrangement to the above,
although on account of the absence of an inner ramus it is
less evident. I believe that the appendage figured at the'
outer apical angle of the furca is intended for a spine, rather
than a seta as Schmeil supposes it to be. From this it will
be seen that the drawings and descriptions conflict, and Dr.
Schmeil was perhaps justified in proposing to establish a new
genus, Lamellipodia, to receive this species. It seems to me,
however, that it would be better to wait until material col-
lected in the same locality and described and figured by a
more careful observer has determined whether or not this
species is a good one, and I have hesitated, therefore, to
adopt a new name for a form the description of which, to use
Marsh's words in regard to Scopiphora vagans Pickering, " is
manifestly inaccurate in some particulars, and maybe in all."

268 Illinois S%(tc Laboratory of Natural History.

ADDITIONS TO THE BIBLIOGRAPHICAL LIST
PUBLISHED IN ARTICLE III.

Birge, E. A.
'97. The Vertical Distribution of the Limnetic Crustacea of Lake
Mendota. Biol. Centralbl., XVII. Bd., pp. 371-374; Abstract, Zool.
< 'entralbl.. IV. Jahrg., Xo. 18 u. 19, pp. 606, G07.

Erlanger, It. v.
"97. I'ber die Chromatinreduktion in der Entwickelung der mann-
lichen Gesehleehtszellen. Zool. Centralbl.. IV. Jahrg., No. 8, pp.
265-278.

Forbes, S. A.
'85. On the Food Relations of Fresh-AVater Fishes: a Summary
and Discussion. Bull. 111. State Lab. Xat. Hist., Vol. II., Art. VIII.,
pp. 475-538.

Fric, A., und Vavra, V.
'97. Untersuchungen iiber die Fauna der Gewiisser Bohmens. III.
Untersuchung zweier Bohmerwaldseen, des Schwarzen Sees und
des Teufelsees. Arch. d. naturw. Landesdurchf. v. Buhmeu. Bd.
X. 74 pp., 33 Fig.; Abstract, Zool. Centralbl., V. Jahrg., No. 5, pp.
158, 159.

Fuhrrnann, O.

*'97. Recherehes sur la faune des lacs al pines du Tessin. Rev. Suisse
de Zool., T. XV.. pp. 489-543.

Loude, Ad.

"'92. Xotatki Karcynologiezka. Kosmos (Lemberg) T. 17. pp.
443-448, 561-565. ( Fide Steuer. '97a.)

Richard, J.
'96. Sur la faune de quelques lacs eleves du Caucase d*apres les re-
coltes de M. Kavraisky. Bull, de la Soc. zool. de France, T. XXL.
pp. 183-185.

Schacht, F. W.
'97. The North American Species of Diaptomus. Bull. 111. State
Lab. Xat. Hist.. Vol. V.. Art, III., pp. 97-207. Pis. XXI.-XXXV.

Scott, Th.

*'98. Diaptomus Jiircus G. S. Brady, in Loch Lochy, Mouness. Ann.
Scott, Xat. Hist., Jan., 1898. p. 55.

Scott, Th., and Duthie, R.
*'97. An Account of the Examination of some of the Lochs of Shet-
land. Fifteenth Ann. Rep. Fisheries Board, for Scotland, pp.
327-333.

All articles except those marked with an asterisk are in the Library of the Mate
Laboratory of Natural History or in that of the University.

Nortli American Centropagidce. 269

Scott, Th., and Scott, A.
'97. Notes on Sunarestes paguri Hesse, and some other rare Crusta-
cea. Ann. Nat. Hist., Vol., 20, pp. 489-494. 2 Pis.

Steuer, A.
'97. Copepoden und Cladoceren des siissen Wassers aus der Umge-
bung von Triest. Verhandl. d. k.-k. zool.-bot. Gesellsch. Wien,
Jahrg. 1897. 16 pp., 1 PI.

'97a. Ein Beitrag zur Kenntniss der Cladoeeren-und Copepoden-
fauna Karntens. Verhandl. d. k.-k. zool.-bot. Gesellsch. Wien,
Jahrg. 1897. 49 pp., 6 Fig.

'97b. Liste aller bisher in Rarnten gefundenen Cladoceren und
Copepoden. "Carinthia" II., Nr. 4. Klagenfurt.

Szekely, B.

»'82. Tanulrnauyok a Diaptomus petefejludcsonek elso phasisairol a
blestoderrna fellepescig. Kolozsvar, 1882. (Fide Steuer, '97a.)

INDEX.

(Synonyms in italics..

Calanus, 237.
Canthocainptus. 225.
Centropages, 244.

hamatus, 244.
Centropages. 235.

grimaldii. 238, 242.
Centropagidae, 225, 227, 244.
Copepoda, 225. 227. 228.
Cyclops. 225.234, 235. 263.
Diaptomus, 225, 226. 227. 228, 230,
234. 235, 236, 237, 250, 265.

ashlandi, 260. 265.

minutus, 260, 265.

oregoneusis, 229. 265.

pallidas. 265.

sanguineus. 234.

sicilis, 229, 264.

siciloides. 229. 265.
Entomostraca. 225, 228.
Epischura, 225, 226, 227, 228, 237.
249, 267.

fluviatilis, 226, 250, 265.

lacustris. 22S. 229, 249, 250. 25 1 ,
252, 254, 255, 256, 260, 267.

nevadensis. 229, 249, 250, 251,
254,255,256,262,264.

nevadensis columbice, 256, 258.
259.

Epischura — Continued.

nordenskioldi. 249. 250, 251.
252.
Euryteuiora. 225.

herdmani. 226.
Heterocope. 225, 267.
Lamellipodia, 267.

fluviatilis. 265.
Limnocalanus, 225, 226, 227. 228,
235.

grimaldii. 226. 229. 236. 239. 243.

macronyx (?). 226.

inacrurus. 226.227. 229. 235, 236,

237. 238,264.
macrurus ductus, 239, 244.
sinensis. 226, 229, 235, 236, 237.

238, 245.
Osphranticum, 225. 226. 227, 228,

229, 234. 235, 237.

labronectum, 227. 230.
Potamoichetor. 229, 230.
Potomoichetor, 229.

fucosus, 230. 233.
Tt mora. 225.

affinis, 225.
Temorell". 225.

affinis, 225.
Scopiphora, 249, 263.

vagans. 260, 263, 267.

BULLETIN

OF THE

Illinois Qtate I aboratory

OF

NATURAL HISTORY,

Urbana, Illinois.

VOLUME V

ARTICLE V.— PLANKTON STUDIES. II. ON PLEODORINA
ILLINOISENSIS, A NEW SPECIES FROM THE PLANK'-
TON OF THE IILINOIS RIVER.

By C. A. KOFOID, Ph. D.

Illinois State Laboratory of Natural History,

URBANA, ILLINOIS.

September, 1898.

State Laboratory of Natural History.

LABORATORY STAFF.

Professor Stephen Alfred Forbes, Ph. D.,

Director of State Laboratory and State Entomologist.

Charles Arthur Hart,

Systematic Entomologist and Curator of Collections.

Frank Smith, A. M.,

Assistant Zoologist.

Charles Atwood Kofoid, Ph. D.,

Zoologist, and Superintendent of Biological Station.

Ernest Browning Forbes, B. S.

Entomological Assistant.

Wallace Craig, B. S.,

Zoological Assistant.

Mary Jane Snyder,

Secretary.

Henry Clinton Forbes,
Business Agent and Librarian.

Lydia Moore Hart,
Artist.

Article V. — Plankton Studies. II. On Pleodorina illinois-
ensis, a New Species from the Plankton of the Illinois
Hirer. By C. A. Kofoid.

The genus Pleodorina was discovered in 1893 by Shaw
('94) at Palo Alto, California, and in May of the following-
year the species Pleodorina californica, upon which the genus
was founded, was detected by Mottier ('94) in water from a
shallow stagnant pool near Bloomington, Imliana. During
the same summer the form also occurred in the Illinois River
and its adjacent waters (Clinton, '94), and it has been found in
the plankton of these situations in succeeding years from
June to September. The distribution of the species in this
continent is thus quite extended, and it is not at all improb-
able that continued investigation of fresh- water plankton will
demonstrate that this genus has a cosmopolitan distribution
similar to that of some other genera of the family Volvocinece
to which it belongs.

On June 16, 1898, a form which may be referred to the
genus Pleodorina was found in the Illinois River in water
entering the stream in large part from Cook's Slough and
Quiver Lake. Owing to high water (ten feet above low-water
mark) prevailing at the time, a considerable portion of the
habitat of the form in question consisted of submerged terri-
tory, with shallow warm water abounding in growing aquatic
and semi-aquatic vegetation.

This Pleodorina could not be found in Quiver Lake collec-
tions made on the 7th of June, but on the 16th it was present
in the river in small numbers, increasing until the 20th, when
a maximum was reached. From this time the numbers
decreased until the 27th, when, following a rise in the river,
the species seemingly disappeared entirely from the plankton.
It was also found sparingly in Thompson's Lake during this
period, a large area of slightly submerged territory being at
this time tributary to the lake.

Associated with this species in great abundance was Eudo-
rina elegans, in all stages of asexual reproduction, and Pando-
rina mormn was also present in smaller numbers and in like

274 Illinois State Laboratory of Natural History.

condition. Volvox, Euglena, Phacus, Lepocinclis, Traehelo-
monas, Dinobryon, Synura, Mallomonas, Uroglena, Melosira,
and Fragillaria occurred in varying frequency, but only a single
specimen of Pleodorina californica was found in collections
containing the species described in this paper. The animal
plankton was represented in the main by rotifers, Polyarthra
being most abundant, while Synchceta, Euchlanis, Pterodina,
Brachionns, and Anurcea were also present. Difflugia,
Codonella, Bosmina, Cyclops and nauplii complete the list
of the more common associates of this Pleodorina in the
plankton.

Pleodorina illindisensis n. sp.

The species here described consists of an ellipsoidal eoeno-
bium or colony of 32, rarely 16 and still more rarely 64,
biflageUate cells. The shape is quite constant, occurring in
the youngest colony and continuing throughout the asexual
cycle until the daughter colonies abandon the gelatinous
matrix of the maternal organism. Among the large number
examined only a few specimens were seen which approached
a spherical form. Measurements of tw r elve seemingly full-
grown colonies from material freshly killed in 2% formalin
showed a range of 101 to 137 /< in long diameter, and an
average of 113 j(. The transverse diameter ranged from 84
to 102 f-i, and averaged 94 /<. Individuals in which the
gonidia have begun to divide show a considerable swelling of
the hyaline gelatinous envelope. One specimen containing
2- and 4-cell stages measured 178x155 //, and when
the young colonies are ready to escape, the parent may meas-
ure as much as 200x175 )t. At the time of escape the
young colonies measure 46x38 /'. The measurements of
the colonies approach very closely those given by Butschli
('80-89, p. 840) for Eudorind; viz., 100-150 n ; and the
colonies of this genus found in association with the form here
described exhibit dimensions almost, if not quite, identical
with those above recorded for the Pleodorina.

The colony (PL XXXVI., Fig. 1) contains, as a rule, 32
cells arranged, as Henfrey \'5i\) first noted for Endorina, in

On Pleodorina Illinolsensis. 275

five circles, two of which are polar and contain four cells
each, while eight cells are found in each of the remaining
three circles, one of which is equatorial and the other two lie
between the latter and the polar circles. The cells resemble
those of Eudorina in that they are situated in the periphery
of the hyaline gelatinous matrix and are not closely crowded
together, the degree of separation depending upon the age of
the colony and varying considerably in different cases.
Their inner ends do not approach the center of the colony as
is the case in Pandorina. No trace of any protoplasmic
connection between the cells of a colony could be detected in
the living organisms, nor in material killed in formalin or in
chromo-aeetic acid and afterwards stained in fuchsin, hema-
toxylin, or Bismark brown. Specimens treated by Zograf's
method (1% osmic acid followed by 4% crude pyroligneous
acid) or by 1% osmic acid followed by picrocarmine, showed
no connection between the cells.

The colony is surrounded by a common gelatinous sheath
(sh.) increasing in thickness (3.5 to 12 /<) with the age of the
organism. This membrane or sheath is of equal thickness in
all regions and consists of two parts : an outer, thin, denser,
more highly refractive layer (o.l.) ; and an inner homogeneous
one (/./.), which shows no traces of the concentric structure
found in Pandorina. It is within this latter layer that
the increase in thickness takes place in the older colo-
nies. It is limited centrally by a thinner and less highly
refractive layer (m.m.) which encloses the common matrix
(m.) in which the cells of the colony lie. Frequently among
the older organisms there occur upon the posterior end of the
colonies blunt, pseudopodia-like protuberances (PL XXXVI.,
Fig. 4) of the sheath, of irregular form and of no constant
number. Their position and the fact that they are often,
though not always, found in old colonies from which some of
the daughter colonies have already apparently escaped, sug-
gest that they may mark the place of exit of the young indi-
viduals from the parent. Similar protuberances were ob-
served upon Eudorina and Pandorina, under similar con-
ditions, in the collections in which the Pleodorina under

276 Illinois State Laboratory of Natural History-.

discussion was found. Wills ('SO) found that the daughter
colonies of Volvox globator escaped through a rift in the pos-
terior hemisphere of the parent, and Klein ('89) observed the
same phenomenon in Volvox aureus. The escape of the
daughter colonies in Pleodorina has not been observed by me.

The sheath stains deeply in an aqueous solution of methylen
blue, more deeply, in fact, than the enclosed matrix, the outer
layer taking the deeper stain. It also shrinks to about one
fourth its former thickness. This shrinkage, together with
that of the central matrix, causes the sheath to wrinkle along
lines which bound hexagonal areas from whose centers the
cells now project, thus giving the appearance of a division of
the surface of the colony into regular polygons. The sheath
shows no trace of the layer of radial rod-like structures
found by Klebs ('86) in Pandorina, but iodine or methylen
blue demonstrates a finely granular condition like that
described for Eudorina. The sheath is traversed by the pairs
of flagella which arise from the outer ends of each of the cells.

The matrix (m.) is a gelatinous substance of some consist-
ency, filling the colony inside of the inner membrane. In
the living colonies, in those which were killed in the
various reagents mentioned above and afterwards stained,
and in disintegrating material, no traces of any divisions can
be detected in this substance that are not due to wrinkling
caused by shrinkage. Methylen blue or iodine causes the
matrix to show a faintly reticulated or vacuolated appearance
due to different densities of staining. That the substance of
the matrix has considerable consistency even in the swollen
condition found in the maternal colonies, is shown by the
fact that the flagella of the young forms, before rotation
begins, can be seen to penetrate the matrix of the parent very
slowly. Their ends are often blunted or even knob-like and
their lateral motion is very limited. The movement of the
young colonies through the matrix is a very slow and gradual
one, showing the gelatinous consistency of the substance in
which they are imprisoned.

The striking feature in the structure of this species, as in
the case of V. californica (Shaw, '94), is the presence of two

On Pleodorina illinoisensis. 277

distinct types of cells in the colony (PI. XXXVI., Fig. 1),
the vegetative (v. c.) and the gonidial (g. c.) cells. The
presence of these two types of cells at once places this new
species in the genus Pleodorina rather than in Eudorina —
which it otherwise closely resembles.

The vegetative cells (v. c.) are four in number and consti-
tute the anterior polar circle, being always directed forward
in locomotion, as in the other species of the genus. Their
number remains the same in the smaller colonies of sixteen
cells