//-A-

BULLETIN

Illinois Qtate j^aboratory

OF

NATURAL HISTORY,

Urbana, Illinois.

VOLUME V.

ARTICLE IV.— THE NORTH AMERICAN CENTROPAGID.E
BELONGING TO THE GENERA OSPHRANTICUM, LIM-

NOCALANUS, AND EPISCHURA.

By FREDERICK WILLIAM SCHACHT, B. S.

Illinois State Laboratory of Natural History,

IKBANA, ILLINOIS.

1898.



State Laboratory of Natural History.

LABORATORY STAFF.

Pi-ofessor Stephen Alfred Forbes, Ph. D.,

Divector 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 Sitperintendent 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.



ERRATA.

Page 136, line 2, and jiage 182, line 17 from bottom, f(jr 'g^a read 'gj.

Page 226, line 2, page 263, line 17 from bottom, and page 267, lines

2 and 15, for 'g8, read 'g6.

Page 233, line 15 from bottom, for '82 read '82a.

Page 355, line 2 from bottom, for C. F. Hudson read C. T. Hudson.

Page 389, foot-note, for Vol. V. read Vol. IV.

Page 457, line 5, for Genera read Genus.

{



Articlk IY.— The Xort]i A)iicrici(ii CcntropiKjuh^- licloiif/iii;/

to the Genera Osphriuitlciim, Limnoealduiis, and Kjt'i.s-

rhiira.* By Frederick William Schacht, B. S.

INTRODUCTIOX.

In Article III. of this Bulletin the writer discussed the

North American species of Diaptomua, and in the present

paper, in furtherance of the same purpose, the genera Os-

phranticiiiii, L'uiniocalanns, and Episehiira are treated. In

the introduction to the former article was given a short

account of the work of Avriters on the Entnmostraca now
included in the family Centropaii'uhe, especially those genera

found in North x\merica. 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 ('88)'. After an
enumeration of the genera of fresh-water Copepoda he says :

"Of these eleven genera, four

—

Diaptomus, Lhnnocahonis,

Cyrlo2)s,?ind Canthoeamptus—have l)een 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 {--^T<'inora-- Teinorclla) [ was per-

haps overhasty in my conclusions, but it being now too late

to remedy the omission, the following statements must
sutfice. In his "Final Report" 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 tlow. In the " Crustacea of Alabama"
('87) he notes, under the name of Temorella affinln, a species

which according to his statement is the same. The figures of

*This paper wax accepted by the Faculty of the University of Illinois .lune 1,

18W, as a thesis for the degree of Master of Science in Zoology.

+The parenthetical tigures in the text of this paper refer usually to the bibliog-
raphy of Article HI., which is, however, supplemented by an additional list appended
to this discussion.

225



226 lUino'iH Stdte IjitJioratorii oj' Xatiiral Jl'n^torj/.

the species in question differ, however, so considenibly in

these two articles that, as Schmeil ('98) says, nothing certain

can be said of this species until Herriek declares himself as to

which of the tw^o sets of drawings are correct. Schmeil regards

Herrick's form as possil)ly a new species. The recent dis-

covery of a new species of this genus, Eiirijtemord hcrdmani

I. C. Thompson and A. Scott, in the St. Lawrence Eiver and

Gulf removes all doubt as to the presence of the genus in

American waters.*

Of the three genera treated in this paper, Osphrani'u-uni,

containing a single species, {indEpisehiird, containing three"-,

are, so far as now known, confined strictly to North America

and are strictly fresh-water in their habitat. Osphranticwit

is ordinarily found in shallow or stagnant lakes and ponds

(Forbes) or in running water (Herriek), while Epischuvd

occurs, as a rule, in deep clear lakes. The genus Limnocalanus

is peculiar in its habitat. One of the two species, Ij. sinensis

Poppe, from China, is, so far as known, a strictly fresh-water

form, Avhile the other, L. inacruviis Sars, although found as

yet in America in freshwater only, occurs in Europe and Asia

in Ijoth 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. [/ri))t(tl(Ul de Guerne is re-

garded by the writer as a synonym of L. macniriis 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 Osplirant't-

ciim, Limnocalcoius, Diaptomus, and Kpischura may properly

precede this paper, special attention being given to characters

wdiich are regarded as of generic or specific value.

Giesbrecht, in his "Monograph" ('92), gives special rank

to the structure of the first pair of antenna as a distinguish-

*See "On the Plankton collected continuously during two Traverses of the Nortli
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.

^E- flavlatilis Herricli is not considered one of these.

iThe Ziologisches ('entratb^att (Jahrg., HI., pp. 481-4S.3) contains a review of an
article by N. Zograf entitled " Essai d'Explication de I'origine de la Faune des lacs de
la Russie d'F;urope"in which a reference occurs to L. macronyx O. O. S. This is

probably an error, since it is the only reference to a species of that name which I

nave been able to find.



XortJi A)nn-ic(in CciifropKi/idfr. 227

ing character in the Cojn'poda. If this be taken as a basis

of chissilication here, Osphvdnticum, with its 23-segmente(I

antennjv, would form a group by itself, while Livinoralanus,

Diapto)iiiis, and Epischnra, with their 25-segmented antennae

would constitute another group.

Osphraiiticum seems to be the most primitive of the Amer-

ican Centropaghhe, 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.

LimnocalauHs apparently approaches most closely to Os-

phranticum, the fifth pair of legs of the female being very

similar in general structure to those of OsphranticiDii, as is

perhaps most strikingly illustrated in the case of L. macru-

riis Sars and (). lahroncdum Forbes. In Llmnocdlanus 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.

Diaptoinus 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.



2*28 IlU)io}s State La1>or((tori/ of N<(tiir<il ll'istorji.

In Eplsrlinra, as in the other three genera, the cephalotho-

rax is six-segmented. All of the s^vimmillg 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 moat primitive form, Fypisrlmra as the most

modified, and Limnocalanus and DuiptovtHs 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 Ospliranticum and Diaptomus

the females carry the eggs in an egg-sac, while in Limnocal-

aiiKS and Episclmra they do not. In OsphranticuDi , Diapto-

mus, ?iwdiEpischuraihe spermatophore persists for 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, and

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 Kiver in China, Newfoundland, and the States

*" The sexually mature individuals are to some extent so transformed by para-
sitism that unless the fertilization by means of spermatophores be excepted they seem
to have no characteristic common to all which would at the same time distinguish tlie

order Copepoda frora the other orders of Entomostraca-'' (Giesbrecht, '!t2, p. -Ul)



Xortli Aimricdii Cnitrojxfifida'. '22W

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-

cJiura laciistris and Dhtptoinus oregoneiiais. 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 Epiarhio-d Uichh-

tris, Diaptomiis aicilis, D. o}'e(joiu'i>>^iH, and 7>. sicilo'uh's, I also

acknowledge my indebtedness to Prof. G. 0. Sars, who kindly

furnished me with specimens of LiiHuorahtniis grliitaldii, thus

enabling me to compare them with L. in<(cn(riis—also fur-

nished by him to the Illinois State Laboratory of Natural

History; to Herr S. A. Poppe, for specimens of Lhiuiocahniiis

sinensis: to Professor Lillejeborg for E])lsrhi(n( iievaden-si-s

;

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 accomj^any this paper, since the species

treated may be identified by figures already published.

OSPHRANTICUM FoRBES.

Osphranticum, Forbes. \S2a, p. G4,5.

Pot.omdichetor*, Herrick, '82. p. 23.

Osphranticum, Herrick, "84, p. 134.

Osphranticum, Herrick. '87, p. 12.

Osphranticum, de Guerne et Richard, "S9b. p. 149.

Osphranticum, Herrick and Turner, '95, p. 85.

Cephalothorax compact, six-segmented, the first two seg-

ments confluent 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 sette, the second from within the longest,

and with a delicate smooth seta on the inner margin of the

*SpeUed Potamoichetorhi Herricks snbsetiuent references.



230 lUhwis State Ijuhitrtitorii of Ndtiduil Histori/.

dorsal surface. First pair of antennae 23-segmented ; right

male antenna geniculate between the 18th and 19tli seg-

ments, and the 19th and 20tli segments ankylosed. Second

pair of antennfe, mandibles, and first, second, and third

pairs of maxilhe as in Diaptoinus, hut stouter. All the swim-

ming legs biramose, with three-segmented inner and outer

rami ; armed with stout sette. 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 labronectum Forbes.

Osphranticum labronectum, Forbes. '82, p. 645, PI. VIII., Fig. 24. 28,

29; Pi. IX., Fig. 1, 2, 4, 5, 7,9.

Fotomoichetor* fucosus, Herrick, -82, p. 224, PI. II., Fig. 12-14; Pi.

III., Fig. 1-8, 13, 14.

Osphranticum labronectum, Herriek, *84, p. 134, PI. Q2, Fig. 1-8, 13, 14.

Osphranticum lab^'onectum, Herrick, '87, p. 12.

Osphranticum labronectum, de Guerne et Richard, 89b, p. 149, Fig. 1.2.

Osphranticum labronectum, Herrick and Turner, '95, p. 86, PJ. XII.,

Fig. 1-8, 13, 14; PJ. LIX., Fig. 7, 8.

Of medium size, body compact, widest before the middle.

Cephalothorax 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

setae 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 Potamoichetor in Herrick's subsequent references.



XortJi . line lied II ( 'ciitropdi/idtr. 'l^M

than any of the t)thers except the tifth, whicli is the shortest

;

the second, third, and fourth set?ments decreasing in k'ngth

in reguhir order ; the second slightly shorter than the furcal

rami, which are armed as in the female.

Antenn;!:' "iS-segmented, extending about to the end of the

eephalothorax, or barely surpassing it. l^ight male antenna

geniculate between the 18th and 19th segments; l*)tli and

•20th segments ankylosed ; six segments preceding the genicu-

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 al)()ut as long as

the segment itself and provided on each 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 spinas, 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 Avhich 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



232 Illinois State Lalioraforji of Ni(tiir((l Hiatorfi.

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

the 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 leg 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 Avith a

few delicate hairs. Third segment considerably narrower

than the second and slightly shorter ; armed at the apex with

two lamellate seta; and a short sharp spine. Inner ramus

like that of right leg.

Fifth pair of legs of female biramose. Second basal seg-

ment iDrovided on the outer margin, a short distance above

the middle, Avith 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 fine hairs ; inner margin sulcate

and armed with four slender subequal plumose setae about as

long as the segment.

Inner ramus of fifth leg of female three-segmented, the

first segment irregular in shape, with a somewdiat projecting



Xorf)/ Amcricdii ( 'tiitroixn/'nh/'. 233

inner apii-al angle. Second segment subquadrate, 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 seta", at the apex with two similar seta- 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 fine 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 ])laces, 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 fucosu h , in

the Tenth Annual Pieport of the Geological and Natural

History Survey of Minnesota (Herrick '82). This Ileport

was not distributed, however, until after the August number
of the "American Naturalist" appeared, which contained the

description of Osphvuntu-um lahronectnm 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 l)y 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 IlU)wi.s Stdtc Lahonifori/ of Natiind Histori/.

lamella on the upper spine of this margin, and the small

spine on the apex of the segment are all omitted. In the

figures of the fifth pair of legs of the male, the small spines,

at the outer apical angles of the segments of both oater 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 tlie

first segment of both inner rami are wanting.

Although this species is widely distributed,—having been

found in Alabama, IDinois, Minnesota, Oregon, and Wyo-

ming,—no differences sufdcient 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 antenna;.

Forbes found the antenna; 23-segmented, de Guerne and

Eichard, who examined specimens sent to Poppe by Forbes,

agreed with him, and the writer also found the antennse of all

the specimens he 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

D. 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 Eiver, in midstream, while in Quiver Lake, in a mat

formed of Ccrdtophyllum and Lemna in a stagnant portion

near shore (substation C), they were comparatively numer-

ous, though not occurring in any such numbers as either

Diaptomus or Cyclops. In fact, in none of the collections

examined were they at all common.

Prof. Forbes, in connection with the original description.



North A)ncric((ii ('ciitrdjiai/uhc. 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 Osphnnitlciim. The following statements,

gathered from observation of a number of specimens kept

for some time in a large flat dish may therefore l)e of interest.

Their movements in the water are very different from the

short jerky springs of Cyclops, and they differ also from those

of l>i(ij>toiiuis in that they are more regular. The motions

of these three genera might perhaps be expressed ])y tele-

graphic symbols as follows : Cyclops, ; Dhipio-

mns, - ; and OHpliranticam,

. Osplirnnticiim swims equally well on the

dorsal or ventral surface, seeming, however, to prefer the

former position. !\s in Diaptomus, the anterior end is ele-

vated in swimming, and the antenna? 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 l)it of

debris, and then make another dash, repeating the perform-

ance until they deemed themselves out of danger.

Since 0. lahronectiim is the only species known, no key

will be required.

LiMNOCALANUS (I. 0. SaRS.

Limnocalanuft, Sars, 'G2, p. 226.

Centropages. de Guerne, '86, pp. 276-285.

Body long and narrow, the front armed with two hook-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 (inacrKrus)

or five {s'tnciisin) 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,



23() J///»o(.s- State Lahordtori/ of Ndtiiml History.

near the inner margin and opposite the outermost of the

other seta'.

First pair of antennae shorter than the bodj^ 25-segmented,

the hist segment very smalh Right 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 sets. First pair of maxillae

about as in l)laptomns. Second pair of maxillie robust,

eight-segmented, the last segment procUiced 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 setae.

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

;

armed 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- {inacriiriis) 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 those of the preceding pair {macrurus),

or differing from one another {sinens'ts). Eye single, near

the lower margin of the head.

This genus was established by Dr. Sars in 1862 to receive

*The parts of the generie description referring to the structure of the second
pair of antennae, the mandibles, maxillae, maxillipeds, and the swimming legs are
compiled from Sars (62 and '97), Xordqvist ('88), and de Guerne and Richard ('89b).

In regard to the second pair of antennae of macrurus the writers mentioned state
that the outer ramus is seven-segmented, and Nord(|vist says further that the suture
between the second and third segments is indistinct, and figures the antenna with six
segments. Sars ('97) says of griinaUUi that the outer ramus is six-segmented and so
figures it. After careful examination. I find no diit'erence in the second pair of an-
tennfe of macrurus and arimaldii, the segmentation being equally distinct, each of
the four spines between the second and last segments marking a segment.



North Ameriraii Coitrojxir/itld'. 237

a fresb-watev ceiitrDpatiid closely resembling tbe marine

genus CaUniKs, and until 1881) L. macniriis was tbe only rep-

resentative known. In tbat year Poppe described (de Guenie

et Richard, '89b) a new species, L. sinensis, from Cbina.

Tbe latter, so far as now known, is a purely fresb-water form,

and L. inacnii-Ks was at first so regarded, but in Asiatic and
European countries it lias been found to occur in l)otb fresb

and salt water,—in America it bas as yet been found only in

fresb water,—and further search may show that L. sinensis,

too, is common to both. L. macriirus is tbe only American
representative of the genus, but it was deemed best to in-

clude sine)isis in this paper, thus making tbe revisicm of tbe

genera treated complete.

As already stated, the genus is represented by only two

species, iii((rn(n(s and siiie)isis. The former is common to

America, Europe, and Asia, having been found in the river

•Tana (in East Siberia), in tbe Caspian Sea, in the Arctic

Ocean, in tbe lakes of northern Norway, Sweden, and Fin-

land, and in the deeper northern lakes of North America

;

tbe 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 lAmiiociihtnus,

and states tbat 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 Liiniio<-((la)jiis has never been found with

an egg-sac, differing in this respect from OspJiiuoitirniii and

Diaptomiis but agreeing with Kpiscliiira. The spermatophore,

a slender tubular structure, adheres to tbe 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 Corcgonns

cliipeiformis (Forbes '83a), of Lahidesthcs siccaliis*, and

prol)al)ly of other lake fishes.

*See Forbes "Ou the Food Relations of Fiesh-Wiiter Fishes: a Summary and Dis-
cussion.' Bull. 111. State Lab. Nat. Hist.. Vol. H., Art. VHI.. p. 53;.'. 18K5.



238 lUniois State Laborntory of Natural History.

Since there are only two species of L'nnnocalanus known,

the key is naturally very simple, and only the most striking

differences are 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 hoth margins with fine symmetrical teeth.

Outer apical angle of same segment armed with a

stout serrate spine. Second hasal 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 fine 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). Eight outer ramus of fifth legs 3 -segmented (third

segment indistinct). Hook-like process of second seg-

ment of this ramus simply and but slightly curved

;

provided with hyaline plate. Inner rami alike.

macrurus.

2 (1). Eight outer ramus of fifth legs clearly 2 -segmented.

Hook-like process of second segment of this ramus
somewhat sinuously curved. Inner rami unlike.

sinensis.

liimnocalanus macrurus Saks.

Limnocalanus macrurus. Sars, '62, p. 226.

Limnocalamis macrurus, Forbes, 82a, p. 049.

Centropages grimaldii, de Guerne, '86, p. 276.

Limnocalamis macrurus, Nordqvist, "88, p. 31. PI. I., Fig. 9-11; PI.

n., Fiff. 1-5; PI. III.. Fig. 1-4.

*In de (Juerne and Richard's "Revision." Fig. 5a iu the description of Plate IV.
should be Fig. 15a. *



Xortli .[))ur'icnn (\iifr(ip<t<i'i<h<'. 239

Limnoealamis macrurus, ile Gueriie et Kichanl, "SOb. p. 77. PI. IV.,

Fijr. 5. 11. 12.

Limnoailanus macrurus auctus. Forbes, "00. ]>. 618.

Lhnnocalanus macrurus, Marsb, '93, p. 201, PI. IV., Fi>i*. 7.

Limnoealamis macrurus. Marsh, '95, p. II, PI. R'., Fi>:;. 1, 2; PI. V.,

¥ier. 1-5.

Limnocalauus macrurus, lierr'ick and Turner, *95. p. 49, PI. I., Fii;;. 1-4.

Limnoealamis (jrimaldii, Sars, "97, p. 39, PI. IV., Fig. 1-lS.

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 downAvard) 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, but

armed on each side with a very small spine. Abdomen of

female composed of four segments, the first about a third

longer than either of the two succeeding segments, which are

subequal. Fureal 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 al)out twice as long as the fifth ; second,

third, and fourth segments armed like the second abdominal

segment of the female. Fureal rami proportioned about as

in the female and similarly armed.

A-nteunte 25-segmented ; right male antenna geniculate

between the 18th 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 IlU)wis K:yt((te LdJioiuitoi-ji 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 hroad seta, a short curved spine,

and a sense-hair; 9, a long l)road 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 ; 13, 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 ol^scurely 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 sets and a sense-

hair; 24 two setse; and 25 (very short), four sets 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-

cond segment slightly narroAver than the first
;
produced at

the inner apical angle into a hook-like process, which is

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 striation. The

hook is fully three times as long as the segment itself.

Inner ramus of right fifth leg three-segmented, the first

segment irregular in form, about tAvice as long as wide;

armed on almost the entire outer margin Avith a feAv fine

hairs, and at the beginning of the distal third Avith a slender

plumose seta. Second segment someAvhat wider than the



Xortli .1 iit( ricdii ( '(iitr()})ii(iiil<c. '241

first, aiul 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 setfie, 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 tjie 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 Avide as the first and

barely twice as long as wdde ; 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 somewdiat nar-

rower than the first and not quite twice as long as w'ide

;

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 La1>or(itori/ of Natural History.

on the inner margins ; inner apical angle produced in the form

of a moderately curved hook armed on hoth 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 hoth margins, and armed on the outer margin, at the

heginning 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 setae, 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 setre, 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 specimens of

L. niacrarus 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. macrnrufi, the type of the genus, except in regard to syn-

onymy and distribution.

The original description of the species appeared in the

"Forhandlinger i Videnskabs-Selskabet i Christiana " (Sars

'62). De Guerne ('86) described it under the name of Centro-

juiges grimaldil ; Nordqvist, in "Die Calaniden Finlands" ('88),

made this a synonym of 1j. macrnrns ; and de Guerne and

Eichard, in their " Eevision " ('89b), acknowledged the cor-

rectness of Nordqvist's view. Recently, howevei', Professor

Sars, in his "Pelagic Entomostraca of the Caspian Sea"

('97), re-established de Guerne's form as a new species of



North Amenran Centrojjagidce. 243

L'nn)io<(d(niii>>, L. (/riiiuddii de Giierne. Exceptfor 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-w^ater 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

estal)lishment 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. niacniriia are given in "Die
Calaniden Finlands " (Xordqvist, '88) and in the " I^evision

des Calanides d'eau douce" (de Guerne et Eichard, '89b),

although in neither publication are they strictly correct. De
Guerne and Eichard'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 setffi on the

apex of the last segment of the outer ramus, while de Guerne

and Eichard 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 Eichard'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, Xordqvist fails to fi'gure the hyaline process on the



244 Illinois State Ij(i})or<itorfi of Natural IHstori/.

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 Eichard 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. macriirus 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. macriirus is the only species of the family Ccntrojjagidce

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. macruriis 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.



Xorfli Amcrirun ( '/iitrojxif/'Khc. 24;")

Limnocalanus sinensis Poppe.

Limnocalamis sinensis, de Guerne et Kichiird, 8!)b, p. 79. PI. \\ .,

F\^. 4, 15, loa, 16.

Limnocalanus sinp.nsis. Horiick ;ui(l Tmner. "95. p. -1!).

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. F ureal 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 setae 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.

Antennae 25-segmented, hardly extending to the base of

the furca. Eight 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:

11 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; 16, 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 Lahordtori/ 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 occupj'ing 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 setae; and 25 (very short), three long plumose

setae 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 setae, 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



XortJi Amrrituut i'ditropuriidw. 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 about

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 a\ itli 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 Avide

;

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 setii;

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 lU'Diois Sf((te Laboratorij <>/ Natural Ilistorij.

teeth. Third segment about half as wide as the second and

approximately three times as long as its greater width; inner

margin sulcate and armed with five stout parallel plumose

set* ; 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 wdder 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 setpe, 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 furcal 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 Kichard's "Revision." I was unable to find the hairs

* Measurements as given in de Guerne and Richard's '

' Revision " (89b).



NortJi .Imrricdii ('viitroiuni'ithc. '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. tnacriirus, that it

might almost he regarded as the type of a new genus, hut

Poppe has not considered the difierences as of generic value,

nor have de Guerne and Richard. Unlike L. mdrriiriis, the

inner rami of the fifth pair of legs of the male although l)oth

three-segmented difi'er 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 noticeahly unlike, the inner rami are very similar.

This species was found in Lake Sitai, China, and in the

"Whangpoo River, which fiows from it, the waters of both of

which are perfectly fresh. To nay knowledge it has not yet

been recorded from any other locality.

Epischura Forbes.

Sco'piphora ( ?), Pickering, "44, p. 62.

Epischura, Forbes. "S'ia. p. 647.

Ejiischura, Herrlck, "83a. p. 384.

Epischura, Ilerrick, '87, p. 13.

Epischta-a, Herrick and Turner. "85. p. 81.

Epischura, de Guerne et Richard, *89b, 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, nordenskidldi) or flexed to the right and provided

with a process on the right side of the second segment {lacuH-

tr'is) ; in the male, straight or very slightly flexed (nordenski-

dldi) or strongly flexed to the right {lacustris, neradensis) ; 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 setne, one slender simple seta at the inner

apical angle, and a stout spine at the outer apical angle.

First pair of antennse 25-8egmented. Right male antenna

geniculate between the 18th and 19th segments; segments



250 Illinois State Lahoratory of Natural History.

19—21,{ind '22 and 23 ankylosed ; antepenultimate segment

unarmed ; segments preceding geniculation very slightly

swollen. Second pair of antennae about as in Diaptomiis.

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- (laciistris, nevadensis)

or three-segmented {nordenskidldi) ; 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 in egg- sac.

Inhabits deep fresh water lakes.

As will be seen from the above, the doubtful E. iiuviatilis

Herrick has not been considered in this description, but only

the three recognized species, laciistris, nevadensis, and norden-

skidldi.

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 nordenskidldi also varying in the latter

respect, having sometimes five and sometimes six spines.

All female specimens of laciistris 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,



NortJt, Ameriran ('cutropari'idd-. 251

and represented in different sections by different species, is

found from Xe\vfoundland 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 EPISCHURA.

Based 0)1 the Chaydcters of the Female.

1 (2). Al)domen Hexed to the right ; second segment armed
on the right side with a process. Furcal set.ne and

spines very broad. Filth leg with last segment twice

as long as the first ; last segment armed wdth seven

spines. lamstris.

2 (1). Abdomen straight; second segment unarmed. Fur-

cal setae 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. neradensis.

4 (3). Fifth legs slender, first segment considerably longer

than wide ; second segment armed Avith a single small

spine ; third segment armed with five (sometimes six)

spines. nordeiiski'dldi.

Based on the Characters of tJw 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.

necadensis.



252 Illinois State Lahoratori/ of Natural Historij.

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 Ricliard, 'tOb, p. 94, PI. 1.

Fig. 36; PI. II., Fig. 15, 23.

Epischvra nordenskioldi, Herriok and Turner, 'Qo, p. 85, PI. XI.. Fig.

2, 5, 9.

E'pischura nordenskioldi. Sclnneil, '98, 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 setfe 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 wide 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 Amcyiniii ('oitrojxiii'nhf. '25 3

ones. Third segment slightly shorter than the preceding;

process very simple, small and inconspicuous, hluntly ])ointed,

extending almost straight hackward ; armed on outer nnirgin,

near the tip, Avith a slight, hlunt protuherance. Fourth seg-

ment unarmed, ahout half the length of the tirst. Fifth

segment ahout as long as the fourth ; armed with a narrow

triangular plate, broadest anteriorly and hluntly rounded at

the apex. Dextral margins of the fourth and fifth segments

tuberculate. Furcal rami about as in the female.

Antennae 25-segmented, extending almost to the base of the

furca. Eight antenna of the male geniculate between the

iHth and lOtli segments ; segments preceding the geniculation

slightly or not at all sw^ollen.

Eight tifth 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, ai'med

near the distal angle with a small spine ; outline of inner

margin sinuous. Third segment long and narrow, with a

broad basal portion aI)out 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 lu-oad

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 Ill'mois State Lahoratorif 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 neradensis.

Fifth pair of legs of the female uniramose, 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. ;+ 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 tl^e original description. The material was a part of that

collected by Dr. C. Nystrom, a member of the Nordenskiold

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

Eichard'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

"Revision" 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 armntu'-e of this segment differs somewhat in different specimens. See on
a subsequent page the discussi(jn in regard to the fifth leg of the female.

1 Having only a few sjieclmens 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. 1 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 set;c excepted, abo,ut a.9 mm.,
and of male I.l 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 1.3.33 mm. in length, while the average length of live 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 be.



NoitJi AmcrlcdH ('('iitr()p<i<ii(J<('. 255

second segment of the right leg, which Schmeil ('98) says he

could not fuid, 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 hinistris

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 liichard, and
Schmeil, have mentioned the existence of a sixth spine would,

however, militate against this assumption.

The male of nordenskwldi 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 Avould alone serve to

distinguish nordenskidldl. Furlher, 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 neradcnsis

and lariistrls. 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 lacHstriH in that the last segment is armed with only live 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 ncra-

densls being much more robust than those of nordenskwldi,

wdiich 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 Lahovdtort/ of Ndtin-al History.

angle of the second segment of the leg of neiutdcnsis, will all

assist in determining the species.

De Guerne and Eichard (89b) make the statement that the

females always have the spermatophore—which they describe

as curved in a semicircle around the abdomen—attached. On
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. laciistris and E. nerndensis the

female, even when mature, is very often found without a

spermatophore,

Epischura nevadensis Lilljeborg.

Epischuni nevadensis^ de Guerne et Richard, "SOb, p. 93. PJ. II., Fij?.

17, 24 ; PI. III.. Fig. 21.

Epischura nevadensis columbice, Forbes,'93. p. 254. PI. XLI., Fio;. 19-21.

Epischura nevadensis, Herrick and Turner, "95, p. 84. PI. XI., Fig.

1. 6, 8.

Epischura nevadensis columhiiv, Herriclv and Turner, "95, p. 84, PI.

XI., 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 sette, of which the inner is the longest,

the other two being about equal. In the male the abdo-



North Ainericdu C'entrojxKjUlce. 257

men is asymmetrical, flexed to the right, and consists of six

segments (furca inchided). 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 lami slightly longer

proportionally than in the female, but similar in other respects.

Antennae 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.

Plight 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 Lahorntorij of Natural History.

lar hyaline plate which near its middle is somewhat produced

and provided with a numher 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 doAvnwards ; 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 wdde 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.

*0n one or two specimens I noticed quite a large tubercle, with a roughened lip,

projecting from the anterior aspect of this segment near the outer proximal angle,
but did not lind it at aU constant.



NortJi Amerlcdn Centro'pagiiUe, 259

nccadensis eoliiinh'ue Forbes; on other specimens collected in

the same localities—Swan Lake and Flathead Lake, Montana
;

and on specimens from Gaml)le'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, l)ut, 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. nevadensls Lilljeborg and E. nevadcn-

sis columh'ue 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 cohnnh'ue 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

coliimhiif ('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 nevadcnsls (de

Guerne et Pdchard, '89b). Forbes refers to it in his descrip-

tion of columh'ue 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 Diaj)-

4omus ashlandi Marsh and with D. mhiutus Lilljeborg.

Epischura lacustris Forbes.

Scopiphora va<jans (?), Pickering. "44, p. 62.

Epischura lacustris. Forbes, '8-2a, p. 648, PI. VIII., Fig. 15, 16, 21-23,

25-27; PI. IX., Fig. 8.

Epischura lacustris, Herrick, "84, p. 131, PI. Q, Fig. 15.

Epischtira lacustris, de Guerne et Richard, "SOb, p. 90, PJ. IV.. Fig.

3, 9, 10.

Epischura lacustris, Forbes, "90, p. 704, PJ. I., Fig. 1-5; PI. II., Fig. 7.

Epischura 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 C\ntro])af/id(e. 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 setae, 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 fiagellum,

while the other two sette 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 tAvice 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.

Antennse 25-segmented, extending to the posterior margin

of the fourth abdominal segment. Eight male antenna slen-

der, geniculate between the 18th and 19tli segments; seg-

ments 19—21, and 22 and 23 ankylosed; antepenultimate

segment without special armature.



26*2 Illinois State Labordtori/ of Natxral History.

Left fifth leg of male nniramose, three-segmented. First

segment 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 fiat

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 fiexed 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 spines

(the upper two smooth, the loAver 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 the

inner margin with one spine, spinulose on the inner margin.

Length of female 1.784 mm. ; that of male 1.376 mm.
The above description was prepared from type specimens,

from Dr. Forbes's slides, from specimens taken in the same

*In one or two specimens I thought I saw indications of several teeth, similar to
those in E. nevadensis, but could not fully satisfy myself of their presence.



Xortii Amcricdit ('ciitrojxu/uhe. '2C)'6

locality as the type,—Normal, 111.,—and from other speci-

mens collected at various times and places in Illinois, Indiana,

and Alicliigan.

This species, the type of the genus, was first descrihed in

the "American Naturalist" (Forbes, '82a), and de Guerne

and Eichard, Forbes, Herrick, and Marsh have since published

descriptions and figures. Scopiphora rdgaiin Pickering is, as

de Guerne and Eichard, Herrick, and Marsh have said,

probably identical with Eplschura lacKstris, but this can never

be definitely determined since the following quotation is all

that has been published concerning S. lutgans.

"Genus Scopiphora, Pickering. Body small. Eye single,

in the anterior margin of the shield. Antennte large, and as

long as in the preceding genus [Cyclops], and has the same

motions in the water. Al)domen terminating in two styles

each with three setfe ; a brush under the last or last three

joints. Ovaries none. Legs spiny.

" S. vagans (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 (Forbes, '82a) was

(lescril)ed as having processes on the second, third, fourth,

and fifth segments. All figures published previous to the

appearance of " A Preliminary Eeport on the Aquatic In-

vertebrate Fauna of the Yellowstone National Park, etc."

(Forbes, '93), including those of de Guerne and Eichard's

" Eevision," were incorrect. In Forbes's paper attention was

called to the fact that the fourth segment was without a

* See Pickering, '44. '



264 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 " Cyelopidae and Calanidse

of Central Wisconsin" ('93), published the first correct figure

of the abdomen, but seems to have been unaware of it, since

in his " Cyclopidfe and Calanidse 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 Eichard

in their " Kevision," 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 Eichard, 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.

E. lacustris is quite common in the North Central States,

being found in the deeper, clearer lakes in connection with

Limnocakmus macrurus Sars, Diaptomus sicilis Forbes, D.



NortJi Amcricdu ('entrajxn/Kh/'. 265

osJihoidi Marsh, 1). jxtUidtis Herrick, or />. siciloidcs, D. ore-

gonensis, and 7>. minKtiia, 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 Herrick.

EpischuraflMviatilis, Herrick, '83a, p. 381, PI. V.. Fig. 10-20.

Epischura fluviatilis, Herrick, "84, p. 133. Pi. Q, Fig. 14-16.

Epischura fluviatilis, Herrick, '87, p. 13, PI. II., Fig. 21-24.

Epischura fluviatilis, (]e Giierne et Richard, '89b, p. 92, PI. 1 A'., Fig.

13. 20.

Epischura fluviatilis, Forbes, '93, p. 254 (foot-note).

Epischura fluviatilis, Herrick antl Turner, '95, p. 83, PI. XIII., Fig.

14-10.

Lnmellipodia [Epischura] fluviatilis. Sclimeii, "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 Diaptomns except

in-the number of furcal sets. 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.

x^ntenna; 2 5 -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 l)eyond 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 tliree

times as long as wide and entirely unarmed. Third segment

slightly longer and broader than the second, tapering to a



26(3 Illinois State Laboratori/ of Niitiiral 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 fiat surface with two

opposable claws forming a foreipate 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, iVlabama.

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. Jluviatilis, and a figure

representing apparently a ventral view of the last thoracic

segment and aJjdomen, 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 this 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



XortJi Americ((n Ceiitropar/iihe. 267

species cannot belong to the genus Ephchnni, as has ah'eady

been pointed out by Forbes ('93, p. 254) and Schmeil ('98),

since the process cannot be homologized with the similar

process in Kpischnrn 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 W'as three-segmented and the right one especially

modified into a clasping organ if E. Jiuviatilia 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 Epischurn, 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. jinviat'dis, 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 htctistrls the first basal seg-

ments instead of being fused their entire length, as in fiuvia-

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 aj)pendage 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, Lnmellipodia, 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 State 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, XVIL Bd., pp. 371-374; Abstract, Zool.

<'entralbl., IV. Jahrg., No. 18 u. 19, pp GOG, G07.

Erlanger, R. v.

'97. Uber die Chromatinreduktion in der Entwickelung der miinn-

lichen Geschlechtszellen. Zool. CentralbL, IV. Jahrg., No. 8, pp.
265-278.

Forbes, S. A.

'85. On the Food Relations of Fresh-Water Fishes: a Summarj^
and Discussion. Bull. 111. State Lab. Nat. Hist., Vol. IL, Art. VIII.

,

])p. 475-538.

Fric, A., und Vavra, V.

'97. Untersuchungen iiber die Fauna der Gewasser Bohmens. III.

Untersuchung zvveier Bohmerwaldseeu, des Schwarzen Sees und
des Teufelsees. Arch. d. naturw. Landesdurchf. v. Bohmeu, Bd.

X. 74 pp., 33 Fig. ; Abstract, Zool. CentralbL, V. Jahrg., No. 5, pp.

158, 159.

Fuhrmann, O.

*'97. Eecherches sur la fauue des lacs al pines du Tessin. Rev. suisse

de Zool., T. XV., pp. 489-543.

Loude, Ad.
*'92. Notatki Kareynologiczka. 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. Kavraiskj^ 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. Nat. Hist., Vol. V.. Art. III., pp. 97-207, Pis. XXI.-XXXV.

Scott, Th.
*'98. Diaptomus hircus G. S. Brady, in Loch Lochy, Mouness. Ann.

Scott. Nat. Hist., Jan., 1893, 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.

*A11 articles except those marked with an asterisk are in the Library of the State
Laboratory of Natural History or in that of the University.



North American C'entri>j)((;/'ul<e. 269

Scott, Th., and Scott, A.

'97. Notes on Sioiarestes jiaguri Hesse, and some otlier rare Crusta-

cea. Ann.Nat. Hist., Vol., 20, pp. 489-494. 2 PJs.

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-uud Copepoden-

fauna Karnteiis. Verhandl. d. k.-k. zool.-bot. Gesellsch. Wien,

•Talirg. 1897. 49 pp., 6 Fig.

'97b. Liste aller bisher in Kiirnteu gefnndenen Cladoceren und
Copepoden. "Carinthia" II., Xr. 4. Klagenfurt.

Szekely, B.

•'82. Tanulmanj-ok a Diaptomus petefejlod(iS(3nek elso phasisair<Sl a

blestoderma fellepesoig. Kolozsvar, 1882, {Fide Steuer, *97a.)