\ ^ i'catning aiib jfabor. ^ # LIBRARY ^ & OF THE ^ ■J University of Illinois. # ^ CLASS. BOOK. VOLUME. ^ ^ I ^ Books are not to bo taken from the Library. ^ ^ Accessions No .3 .^'J,.!?..':] § Referring to ►r ^""'-'Shers. THIS binoing'^.'^:'^^'^'"^!'- /..v;i f/^-stLf'., SneciaMics.l •V V i. Digitized by the Internet ArchivQ .in 2013 http://archive.org/details/onfreshwatercopeOOshar 4 4 ON THE fresh-watt^:r copkpoda OF THE CENTRAL AND WESTPIRN UNITED STATES OF AMERICA. By Richard W. SJiarpe. Thesis For the Degree of IN THE COLLEGE OF SCIENCE, UNIVERSITY OF ILLINOIS. B. S 1 8 9 5. ( ?^ 3 ON THE FRKSH-WATKK COPKPODA OF THE CENTRAL AND WESTERN UNITED STATES OF AMERICA. Introductory. Our copepod fauna, l^s as yet received little, excej^t local, attention. Hoping to extend our knowledge of the order, especial- ly in Illinois, I iiere present tiie results of my short study of these forms, with a few general introductory remarks. Glaus, Brady, Sars, Lilljeborg, De rrueme and Richard, and Vosseler, of Europe, witli Forbes, Cragin, Say, and Herri ck, of A- merica, comprise tlie list of our most active recent workers on this part of our fauna. Some work lias been done on the lieterogenetic relationships of wiiat are now called distinct species^ and wlien we consider the metamorphoses through which copepods pass before reach ing maturity, the possibility of such relationships is evident. These me tamo rpi loses and the close inter-gradation of related spe- cies cause great confusion, ^larked variations are also known to be ^Herrick, in Amer. Nat. Vol. VII., pp. 208, 581, 2 broiiglit abo\^t hy differences in the character of the liatoitat and tiirough biological relationships, i'rom tiie above causes most of the copepod synonymfv has arisen. So far as I can determine from my reading and observation, no mature Cyclops exists having swimming rami with only two seg- ments. The individuals iiaving sucli rami are usually found in tfaat stage just preceding tlie adult, and may commonly be distinguished at a glance by the fluctuating chiaracter of their antennal segnent?|- tion, and the coagulated appearance of alcoholic specimens. Cer- . tain variations in tlie segmentation of the antennae seem to be due | to age and adaptation. Vosseler (15) notes tlie finding of Cyclops pulchellus Koch at one time with scarcely any apparent antennal segmentation, at anotlier, with antennae of sixteen, seventeen, or even eighteen, segments. Cyclops peramatus Cragin seems to have been described as a distinct species uj-ion some such variation, as it primarily differs from C. pi-ialeratus Koch in having 11-segment- ed antennae. In a single collection, adult specimens of this form were found by me having both 10- and 11- segmented antennae, which, it seems to me, ought to render untenable any specific distinctions on this basis alone. ■•^This and similar parenthetical numbers in tJie text and in the list of synonyms indicate the published work referred to, its name being found against a corresponding number in tlie bibliograpiiical index appended to this paper. The occurrence of a "sense club" on the 12th antennal segment of some Cyclops ha,ving 17-segmented antennae may be of considera- ble importance; but if this is a sense organ and only found in a comparatively fevr privileged species, the question arises, "Why are closely-related species dei)rived of it?" A circlet of short hairs on the basal segment of the antennae also seems to be a dis- tinguishing mark in some species of Cyclops, as, again, a ridge, either serrate, hooked, or plain, on one or more of the distal seg- ments. (See PI. HI., Fig. 15, and PI. V., Fig. 27.) B i o 1 o g i c^a^l. The genus Cycloi>s is found in nearly all parts of tlie world, the temporary pool as well as the permanent body of water afford- it a suitable breeding place. Standing or slowly running water seems to suit these crustaceans best. In ponds especially, they tlirive to perfection, where they often grow to three or four times their ordinary size in other waters. In an examination of material "by me from ponds near Normal, IlJ.inois, Cyclops insectus Forbes was found varying in length from 1 mm. to 5,5 min. Deeper and larger bodies of water commonly afford smaller, more slender, and semi-transparent copepods, this variation being 4 probably due to the greater territory necessarily covered by them in seeking a food supply and their need of protection from tlieir enemies. Cyclox^s tliomasi t'orbes and Diaptomiis sicilis Forbes are both preeminently deep-water forms, and are cases in point. Epi- scl-aira was found in i)emanent bodies of water, wltile Osphranticiim and Canthocamptus seem to inliabit the siiallower, or less stable, pools and ponds. The food of the Copepoda is mainly composed of plant and ani- mals remains, j^rotozoans, and parts of tlie leaves of water plants picked up from tlie bottom or from rocks. Copepods are nearly always found in association with the Os- tracoda, Cladocera, and HydrachJiidae , and are an important element in tlie food supply of most of our fresh-v/ater fishes. Living, as they do, in the siiallower and weedier tracts, tliey are at once a- vailable for tiie fry of such f islies as make these j^laces their breeding grounds, as do most of our fresh-water species. The organic relationsliips of the Copepoda, both near and re- mote, are indeed very complex, and afford the student of biology a very fruitful subject for practical investigation. Their func- *For a brief discussion of thiis question see an article by Professor Forbes entitled " The Lake as a Microcosm," p. 87 Bull. Scientific Ass'n Peoria, 111., or p. 11 Separate. tion in the aquatic balance of organic life is -in important one, as lias been demonstrated by Professor Forbes in investigations on the food of some of our most important food fishes.* Th^ essentials to a /thorougli study of this important order, either /systematic or biological, are a variety of collections cov- ering wide range of territory; and thf; time, ox>portunity , and J surrorimdings favorable to extended work. Though little attention has been bestowed upon the distribu- tion, relative abundance, and economic importance of the Copepoda, yet in tlie systematic line, as well as in economic and philosophic questions pertaining to tliis order. Professor Forbes has oi)ened up a wide field of investigation, with valuable results, while Cragin and Herrick liave added to our knowledge of tlie Copepoda of the Mis sissippi Valley, Massac]uisetts , and Alabama. In 188r., Professor L. M. Underwood published a "List of the Described Species of Fresh-Water Crustacea from America, North of Mexico." At tliat time the Copepoda had been studied only in the eastern United States (Massachusetts), the Mississippi Valley, and *"T]Le First Food of tlie Common Whitefish." Bull. 111. State Lab. Nat. Hist., Vol. I., No. 6, p. 95. S- y 9 e in a t i c. 6 a few scattered localities. The following list is a reyjroduction of the table of the distribution of copepod species in the United States and the Great Lakes as knov/n in 1886 and given by Mr. Un- derwood, to v/hich I Mve added in a parallel column the number of species nov/ knovm to occur in the same localities, so far as I have been able to ascertain. Locality. 1886. 1895. Alabama 7 7 California 1 6 Colorado 1 1 Connecticut 1 1 Illinois fi 21 Indiana 1 2 Kentucky 4 4 Louisiana 8 5 Maine 1 1 >4assachusetts 11 11 Michigan 4 4 Minnesota 24 27 Montana 2 New York 4 4 Ohio 1 1 Wyoming 6 Washington 1 1 Wisconsin 1 8 Lake Superior 2 10 Lake Michigan 4 6 Lake Erie 1 1 Lake Ontario 1 1 Lake Huron In 1886, eight families, fourteen genera, and sixty species 7 were listed, inolnrting the parasitic forms. Deducting the latter there remain three families, seven genera, and forty species of the free-living forms, as follows: I. FAI^ILY CALANinAR. (1) Genus Pi apt onus Westw, 1. _[)_. armatus Herrick. 2, J), kentuckyensis Chambers. ^. T). leptopus Forbes. 4. D_. longicornis Herrick. 5. T]_. minnetonka Herrick. 6. D_, pallidus Herrick. 7. n.. sanguineus Forbes. R. IK sicilis Forbes. 9. D_. stagnalis Forbes (2) Genus Fpischura Forbes. 1. lacustris Forbes. 2. E_. f luviatilis Herrick. (5) Genus Limnocalanus Sars. 1. Lj macrunis Sars. (4)Genus Osphranticum Forbes. 1. 0, lab rone c tun Forbes. II. FAMILY CYCLOPIDAK. (5) Genus Cyclops Mill. 1. C^. agilis Koch. 2. C_. ater Herrick. C^, brevis}:)inosus Herrick. 4. C^. diaphanus Fiscl^er, 5, elongatus Cla\is. 8 6. C. f imT^riatiis Fischer. 7. fluviatilis Herrick. 8. c^. insectiis Forbes. 9. c. modestus Herrick. 10. c. navicular is Say. 11. c_. naviis Herrick, 12. c. oithonoides Sars. 15. c. parens Herrick. 14. c_- pectinatus Herrick. 15. c. phaleratus Koch- 16. ^. pulchellns Koch. 17. serriilatus Fischer. 18. tenuicornis Clans. 19. 1 1 loma si Fo rb e s . 20. c. nniangnlatns Cragin. 21. c. viridis Fischer. 22. c. ingens Herrick. III. FAMILY HARPACTIDAE. (6) Genns Cant ho camp t us Westw. 1. C. cavernanun Packard. 2. C_. illinoisensis Forbes. 5. C. minntns Baird. 4. C. mi nne sot ens is Herrick. 5. C_. northnmbricns Brady var .americanus Kerr. (7) Genns Tachidius Lillj . 1. f onticola Chambers. Many of tlie above species have never been fonnd or identified since first described, while others are known to be bnt synonyms. All of tlie above genera are represented in Illinois with the exception of Tachidius, which iias as yet been recorded only from Kentucky-* Of the twenty-one species of Cyclops recorded, six have *Jonr. Gin. See. Nat. Hist., IV., p. 47 (1881). 9 been found and identified by me,''*' t}ie remainder not occurring in Tl3.inois waters, as far as yet known. The greater number of the above species are reported and described by Herrick (10,12) as com- mon to Minnesota, but most of them lack identification by others tJ:ian the original describer. Judging, however, from the different forms to 1)6 foimd even in our wells, a great number of varieties are to be expected which grade into one another so closely as to be a puzzle to tlie systematist. Little iias been done in the way of a classification of spe- cies. Rehburg sought to classify his species of Cycloi)S under three groups, while Vosseler (15) tliinks that a separation into two groups at least is justifiable. The first of his groups includes all Cyclops Jmving tliree setae or spines on the apical segment of the feet of the fifth pair, wliile the second group includes all having two setae or spines on this segment. Tliis classification, witii some necessary revision, i)f\s been essentially adopted by me, and appears in the key at the conclusion of this paper (p. 52). *See Table of Geograpliic Distribution, p. 48. FAj^/IILY CYCLOPinAK. Cyclops sp . (1) . (PI. I., Figs. 1 — 6.) A small species, but 1,15 mm. long, witli 17-Jointefl antennae, wliich, extended, barely reach to tlie second cepiAlothoracic seg- ment , Tiie first cephalotiioracic segment as broad as long (.55 mm.), equaling tlie following four segments, v/hicl. rapidly taper as a se- ries to uiiite with the abdomen. First abdominal segment mfuch di- lated or tumid anteriorly, tapering posteriorly, and equaling the three following segments, these being subequal and serrate posteri- orly, the last segment shortest, and the serrations having the character of spinules. Caudal rami slender, five times as long as wide, and more than equal to the preceding two and a half abdom- inal segments. Fach ramus witli a stout, broad, knife-like spine at at the outer distal angle about one tliird as long as the ramus; a small slender seta at tlie inner angle sliglitly longer \(one sixth the length of the third from within), wlach for Jialf its length is stout and bare, with nearly parallel sides, the remainder tapering gradually and finely plumose; second seta from witliin of the same character, except tiiat it is as long as the abdomen and furca, and sparsely setose along the inner margin of the basal lialf . 11 Antennae, short, rather stout, and well supplied with long se- tae. As with many other species with 17- jointed antennae, this one has a lanceolate, spine-like "sense cluh," or modified bristle, be- sides the ordinary bristle at the outer apical angle of the twelfth antennal segment. All the joints of the antennae are short and thick, the last three joints equaling tl^ie preceding seven. Anten- nules stout and reaching half the length of the antennae. Latrum with ten teeth. The armatures of the apical segments of the outer and inner ra- mi of tiie thoracic legs are as follows: First Pair. Outer ramus. Inner ramus. Kx., three spines (one ap' parent ly at tip). Kx. ,one seta. Ap. ,one seta, one spine (stout). In. ,tliree setae. A5.,two setae (Fig. 6). In, , two setae. Second Pair. Outer ramus. Inner ramus. "^'X . , ti ire e sp ines . Ap,,one spine, one seta, In., three setae. Ex. ,one seta. Ap. ,one seta, one spine (stout). In. , three setae. 12 Third Pair. Oiiter ramis. Inner ramus. Kx,, three spines (one aj)- Ex., one spine (broad, stout). parently at tip). Ap, ,two spines (broad , equal ) . Ap.jOne sjjine (long, stout). In. , three setae. one seta. In . , t hr e e s e tae . Fourth Pair. Outer ramus. Inner ramus, Ex., three spines (one ap- Fx. , one spine. imrently at tip). Ap. ,two spines (eaual). Ai).,one spine (long). In. , two setae ( slender , short ) . one seta. In., three setae (short). The apical segments of both rami of the second, third, and fourth pairs are as long as the remaining two segments; the spines are unusually stout, wide, and coarsely serrated, wliile the setae are, on the contrary, slender and short. Keet of the fifth pair jointed; apical Joint about a third as wide as the basal and nearly as long; basal joint bearing a short slender seta at its outer distal angle, and the apical witii a short lanceolate spine at its inner distal angle and a short slender se- ta (as long as the preceding one) at its outer. (Fig. 4.) Tiiis species is quite readily distinguishable by the peculiar 15 fom of the caudal setae, the broad coarse spines of the thoracic legs, and tlie short antennae. Described from several specimens collected in July, 1891, a- long t]-ie shores of Lake Minnetonka, Minnesota, among rushes and lily pads. (Mr. H. s. Brode collector.) Cyclops sp . (2) . (PI. II., Figs. 7—12.) This species is rather slender in all its details, with 17- segmented antennae which reach scarcely to the third cephalothorac-' ic segment. Jjength, exclusive of caudal setae, 1.5 mm. First ceplialotlioracic se^^ment very long, one fourth longer tlian the remaining segments of the cepmlothorax; the following three subeciual, tapering to unite with the narrow abdomen. First abdominal segment equaling the following three, with the anterior half tumid in the female; the last segment about two thirds the length of the preceding, narrow, and armed with a row of spinules posteriorly. Tlie caudal rami are narrow, parallel, in width one seventh of their length, and equaling the preceding two and one rourtli seg- ments. The inner terminal bristle slender, five sixths the length of the ramus, and one and two thirds tlie length of the outer bris- 14 tie, which is somewliat stouter, and one fifth the length of the third from within, wiiich is two thirds the length of the second |i from within. Ml are slender and weakly pinnate. Antennae ratiier elongate, the third and sixth joints equal, the last two equal, each twice as long as the fifteenth, while all three fully equal the preceding seven segraents. Tiiere are no spe- cial marks of distinction on the antennae otiier tliari a "sense club"' on tlie 12th segment. Antennules ratiier slender, witli long bristles at tlie end. Labrum with twelve ratlier prominent teetix. Apical segments of thoracic legs armed as follows: Kirst Pair. Outer ramus. Inner ramus. Ex., two spines (one spine at tip) . Fx. ,one seta. Ap.,one seta, one spine (prom Ap.,two setae (slender). Kx,, two setae. inent ) . In., three setae. Second Pair. Outer ramus. Inner ramius. Kx,,two spines. Ap.,one spine (long as Fx. ,one seta- Ap. , one seta (inner angle). J'egment), one seta. In. , three setae. One spine (slender). In. ,tliree setae. 15 Third Pair. Same as second pair. Fourth Pair. Outer rarrnis. Fx., two spines. Ap.jOne spine, one seta. In,, three setae. Inner ramus. Fx. ,one seta, Ap,,two spines (nearly equal) In., two setae. Legs of the fifth pair jointed; basal joint, in width tiiree times tiie length, witii the outer apical angle slightly produced, and bearing a slender naked seta slightly over twice the length of the apical joint, which in width to length is as one to three, and bears two rcearly equal plain setae, little longer tiian tiie preced- ing. Closely related to species (4), but differing in tiie propor- tions of the abdominal segment, of the caudal setae, and in tlie pro portionate lengtlis of tlie antennae, and in the absence of the trans verse row of spines of the caudal rami, which is so characteristic of thomasi . Described from several specimens received from Mr. Chas. C. Adams, whicii were collected from ponds near Bloomington, 111. Cyclops sp . (8) , (PI. III., Fig. 16.) A stovit, robufst species ^with long narrow fiircal rami and 17- jointed antennae which reach but to the second cephalotiioracic seg- ment. Total leiigtli,2 rron. Cex)halo thorax, 1.05 mm. long and .7 mm. wide; abdomen, .4 mm. long, and f urea .2 mFi- — togetiier more than e- qualing the longest bristles. Labnuri witii nine prominent teeth. i Antennae not distinguished by any unusual proportions, but much resembling those of viridis Fischer, with tiie exception tliat the last three segments of viridis are equal to tlie five and a half preceding segments, while in my species (8) tiiey equal the seven and a half preceding segments. The last antennal segment but one third as wide as long, and but a nidiment of the usual sense club on tiie twelfth segment. The laasal joint is as long as the three and a half follov/ing, wi.ile the third is only about one third the length of the foiirth, which is equal to the second and third together. Antennules slender, reaching to the tenth antennal segment . Armatures of apical segments of thoracic legs as follows: Tlie apical segments of tiie outer ramus of the legs of the first pair nearly as broad as long, witii two setae at tip, two spines without, and two setae within; tiie inner ram\is with one spine and one seta at tip, one seta witiiout, and tj.ree within. 17 The apical segrients of ti^e legs of the remaining pairs only about half as wide as long, while in _C. viridis they average three fifths as wide as long. Legs of tlie second pair with one stout spine and one se- ta at the tip of tiie apical segment of the outer ramus, tiiree stout spines without, and three setae within; iniier ramus like that of the preceding pair. Outer ram(»iR of the legs of thh third pair like that of the sec- ond; inner ramus witli two spines at tip of tlie distal segment, one spine witiiout, and tiiree setae within. Outer ramus of legs of the fourth pair like o\iter rami of the two preceding pairs, wiiile the inner ramus has two spines at the tip of the apical segment, one spine without, and two setae with- in. (PI. III. , Fig. 18. ) The second segment of the inner ramus of all the thoracic legs Jrias two setae on the inner side, and all are lanarmed on tlie out- side. The emargination between tl^e segments of the legs is very marked, the indentation amounting to about ItP^-lf the entire width of the segments. Legs of the fifth x^air jointed, the basal segment half as long as wide, tlie outer part lobed, find bearing at its tip a long seta. The apical segment is about as long as the preceding, in width to 18 T length as two to four» and bearing on its outer side, near tlie tip, a short lanceolate spine, and at the tip a seta about as long as the first. Abdonen slender; f ureal rami long and slender, eaualing the last three segments of the abdomen, parallel, and but one sixth as wide as long. fin C^. viridis they are one fo^irth as wide as long.) Inner terminal bristle slender, and one half the length of the ra- mus; outer terminal bristle coarse, spine-like, and about one sixth shorter than the inner one. The longest furcal bristle e- quals the abdomen with furca, and together they equal half the to- tal length of the Cyclops, or, 1 mm. The posterior margin of the last abdoninal segment with a row of spinules. With the exception of species (1), tiiis is the only Cyclops known to me having a spine as the outer armature of tlie inner ramus of tlie third and fourth pairs of legs. Described from several specimens taken by Professor Forbes and party of assistants, under the auspices of the United States Com- mission of Fish and Fisheries, in Lake Winnebago, Wisconsin, June , 1892, where it is everywhere common in association with C. edax Forbes. 19 Cyclops sp . (4) . (PI. IV., Figs. 20— J^4. ) Length, 1,5 mm. • Antennae 17- jointed, just reaching to the end of the first ceplialothoracic segment. The first cejiirialo thoracic segment equals the following four segments, wiiile tiie first abdominal, equals the following tiiree segments in length, is moderately broadened anteriorly, and .18 mm. long. Abdomen (with furca), .5 mm. long and .1 mm. wide. Each abdominal segment bordered posteriorly with a row of ser-| rations, that of the last segment having the cliaracter of fine spin ules; last segment two thirds as long as the preceding one. Cauda]j rami .1 mm long, and in width to length as three to eleven, equal- ing the last two abdominal segments, and bearing on their upper up per outer third two or three minute point-like S])ines, somewhat Of the character of those on the caudal rami of _C. thomasi, Ramal bristles short, slender, finely plumose, the inner bristle about as long as the ramus, two sevenths tj-ie length of ti:ie second from witJiin, which is one and one tidrd the length of the third from within, and proportionate to the outer as seven to one, the oui »r being about half the length of the ramus. Antennal segments short, the last three equaling tlie preceding seven; sense club and seta at the posterior outer part of the twelfth segment; otherwise no special markings. Segments sixteen 20 and seventeen equal, fifteen, half as long as sixteen. Apical segment s of the thoracic legs amed as follows; First Pair. Outer ramus, Inner ramus. Kx.,two spines. Ap., two setae. In. ,two setae Ex. ,one seta, Ap.,one seta, one spine, In., three setae. Second Pair. 0\iter ramus. Inner ramus Ex., two spines. Ap.,one spine, one seta, ( eqiaal ) . In., three setae. Ex. ,one seta. Ap.,one seta, one spine, (equal) In. , three setae. Third Pair. Same as second pair. Fourth Pair. Oixter ramus. ^x.,two spines. Ap.,one spine, one seta. In . , t iiree se tae . Inner ramus. Ex. ,one seta. Ap.,one seta ( spine-like J , one spine, (equal). In. , two setae. The fourth legs tlius differ from those of thomasi in having the apical spine and seta of the inner ramus equal, and in the pro portionate widths of the apical segments of this pair, wiiich in 4 21 thomasi is not more than a fifth as wide as long. Feet of the fifth pair jointed; basal segment somewliat quad- rate, Ixalf as long as wide, the outer distal angle being produced, and bearing a slender seta about four times as long as the seg- ment; apical segment long, narrow, sides somewhat sinuate, length to breadth as four to one, the outer apical angle sliglitly pro- duced and bearing a slender seta as long as the preceding, the in- ner angle bearing a setose seta, somewliat stouter but no longer, I Described from specimens taken from a temj)orary pond south of \ Urbana, 111., Apr. 15, 1892. Cyclops sp ,(5), (PI. v., Figs. 25 — 50.) A small, well-marked species, with seventeen- jointed anten- I * nae reaching just to the third cephalothoracic segment, the last segment with a ridge having a semi-lunar iiook-like notch (Fig. 27), long, narrow abdomen, J^nd slender caudal setae as well as setal ar- maturejof the thoracic legs. Length, exclusive of tjie caudal setae, 1.1 mm. Cephalotiiorax, .65 mm, long, .55 mm. wide; abdomen and furca, .45 mm. Basal segment of the antennae equal to ti^e following three seg- ments; with no special markings and no circlet of hairs. Twelfth segment without a j^rominent seta or sense club. Segment fifteen / 22 two thirds the length of sixteen, which is a fourth longer than the seventeenth, all three equaling the preceding seven. Antennules nearly half the length of the antennae. Lab rum with twelve teeth. The armatures of the thoracic legs are remarkable for the width and prd)i7iinence of the apical si)ines and the slenderness of the setae. First Pair. Oiter ramus. Ex,, two spines (slender), Ap, ,two setae. In, , two setae. Inner vamxs. Kx. ,one seta, Ap.jone seta, one spine (broad, coarse) . In. , three setae. Second Outer ramus. Ex., two spines (broad, one apyvarently at tip), Ap. ,one gpine (long, broad) , one seta (slender). Pair. Inner ramus. Kx,,one seta, Ap. ,one seta, one spine (long, Coarse) . In, , three setae- Third Pair. Same as second pair. Fourth Pair. Outer ramus. Inner ramus, Kx.,two spines (coarse). Kx.,one seta. Ap, ,one spine ( long, coarse ) , Ap.,two spines (inner half length one seta (slender). of outer). In,, three setae. In., two setae (slender). Feet of the fifth pair small and jointed, the basal segment five eights as long as wide, bearing a slender seta, four times as long as the segment, at the slightly produced outer angle; apical segment as long as the basal is wide, narrow, produced, and bearing a long slender seta, over four times as long as the apical segment, and a somewhat coarser setose seta, about the same length, at the middle inner side of tiie same segment. (Fig. 28.) I know of no otlier species having the peculiar crescent- shaped hook on the last antennal segment, or with the fifth feet of] such characteristic shape. The spines of the second, third, and fourth pairs of legs are also unusuf\lly coarse. Described from several females taken by Mr. H. S. Brode from a pond, full of water lilies, rushes, and Anacharis, near Lake Har- riet, Minnesota, July 15, 1891. Cyclops edax Forbes. (PI. VI., Figs. 51--56; PI. III., Fig. 15). 1887. Cyclops edax Forbes, (15)^ p. 709, pl.TTl.,fig. X5; pi. IV., figs. 16—19. A medium-sized species, with caudal setae well developed, 17- jointed antennae, reaching nearly to the fourth ceplialo thoracic segment, the last segment being characterized by a coarse serrate, or notclied, ridge (PI. in. , Fig. 15) . Setae on the outer distal *See foot-note, p. 2. angles of segments one, four, and eleven long and stout, a long sense club besides seta on the twelfth segment, and a short blunt spine on the sixt|> segment; otherwise no special markings. Basal segment of antennae long, equalinj^ tlie following four segments, sixth sli^^Jitly longer than the third, and the seventeenth slightly longer than the fifteenth and just equal to the sixteenth, all three equaling the preceding five and two thirds segments. Total length, exclusive of caudal setae, 1.4 mm. Cephalotho- rax .85 mm.; abdomen .57 mm. First cepiialothoracic segment .55 mm. long and. 4 mm. wide, equaling the three following segments, which are almost subequal, the middle one perJiaps the longer. First abdominal segment eqiials the following three segments ^ seven tenths as wide as long; the last segment the shortest, bor- dered posteriorly by a row of rather coarse spinules. Caudal ra- mi somewliat divergent, rather short (equaling the preceding one and a half segments), the width about one tMrd the length. All the caudal bristles well developed but short, the third from with- out »or longest, scarcely longer than the furca with the last three abdominal segments; the second from without eight ninths as long; the inner scarcely longer than the first abdominal segment; while tiie outer is to the inner as one to two. =F 25 Thoracic legs armed as follows: First Pair. Oiiter rarmis. Kx.jtwo si)i7Tes (one ap- parently at tip), Ap-,two setae. In. ,two setae. Inner rannus Ex., one seta. Ap,,one seta, one spine, (equal) In., three setae. Second Outer ramus. Ex., two si)ines (one ap- parently at tip). Ap.,one spine, one seta, (both long) . In. ,t]iree setae. Pair. Inner ramus. Ex., one seta, Ap.,one seta, one spine (long as segment ) . In.,tiiree setae. Third Pair, Armed like the second. Fourth Outer ramus, %.,two sx>ines (one ap- parently at tip). Ap.,one sx^ine (long, nar- row) , one seta. , In., three setae. Pair. Inner ram^is. Ex. ,one seta. Ap.,two spines ( inner two thirds lengtli of outer. In. , two setae. Feet of the fifth pair jointed, the basal segment rather broad pr than long, bearing at the produced outer apical angle a short slender seta about six times as long as the segment; apical segment 26 as long as the basal but scarcely as inroad, the outer apical angle j being produced, and bearing a long, slender, plain seta three times | as long as the preceding one, while the inner apical angle bears a plumose seta, longest of all. (Fig. 54.) This species has seemingly a wide range of distribution in the United States. Cyclops insectus Forbes. (PI. VII., Figs. 57 — 42.) 1882. CyclOT)S insectus ,Forbes , (9) , p. 649- 1884. " • Herrick, (12) , pp. 151— 152, pi. U. , fig. 9. 1886. " " Underwood, (14) , p. 550. A variable species, measuring (exclusive of caudal setae) from 1.1 mm. to 4 mm,, the cephalothorax being to tiie abdomen as eleven to six. First segment of the cephalothorax about equal to tiie tliree following segments. Last abdominal segment bordered posteriorly by a row of small spinules. Caudal rami four times as long as wide, fully equaling the last two segments of tiie abdomen. Outer caudal seta shortest, iialf the lengtli of the ramus; tiie inner, a third lon- ger than the outer; the third from within four times the length of tiie inner, and tiiree fourtlis tiie lengtii of tiie longest. Antennae seventeen-jointed, reaciiing to tiie middle of tiie sec*-! ond cepiialotiioracic segment. No circlet of liairs; sense club and 27 seta on tiie twelftii segment. No unusual proportions of antennal segments. Thoracic legs amed as follows; First Pair. Outer 3?araus, Inner ramus. Ex., two spines. Ap. ,one spine, two setae. In., two setae. Fx., one seta, Ap,,one seta, one spine (coarse)^ In,,tiiree setae. Second Pair. Outer ramus. Inner ramus. Ex., three spines. Ap,,one Spine, one seta. In. .three setae. Fx. ,one seta, Ap,,one seta, one spine. In. ,ti.ree setae. Third Pair. Armed like the second. Fourth Pair. Outer ramus. Inner ramus. Ex., three spines. Ap.,one spine, one seta. In,, three setae. Fx., one seta. Ap,,two spines (inner smaller). In,,tv/o setae. Fourth pair of feet also characterized by a peculiar narrowing of the basal segment of tiie inner ram^is. (PI. vu.^Fig. 41,) 28 ][ ii ■ii Feet of the fifth pair segmented, the apical segment spmewhjit longer tiian tlie basal and half as wide, with one short spine half the length of the segment and one seta, six to seven times the length of tiie spine, at the tip. Outer distal angle of the basal segment produced, bearing a seta about tiie same length as tJie first The fifth feet resemble those of C_. tiiomasi Forbes and C. vi- ridis Fischer, except tliat tlie small spine is shorter than in tiiom- asi and longer tlian in viridis . The two median caudal setae are also more nearly equal tiian in thomasi , resembling tliose of viri - dis ; but tiie rami are much longer and more attenuated in insectus . This is the most variable sjiecies yet found by me, ranging in lengtli from 1 to ^ rmm Abundant in ponds throughout central Illinois, Cyclops gyrinus Forbes. (PI. VIII. , Fig, 45; PI. III., Fig. 19.) 1887. Cyclops gyrinus , Forbes, (15), p. 707, pi. II., fig. 9; pl.TTT.,fig. 14. 1891. " ■ Forbes, (18), index. A robust species, witii 17- jointed antennae, tlie last tiiree joints being ci-^aracterized by a knife-like ridge, tliat of tiie last joint faintly serrate (Fig. 45). Basal segment of antennae witli a weak circlet of hairs; twelfth segment witli sense club. Kach side of ti.e fifth tlioracic segment furnished witli 29 three transverse rows of minute spinules, much less prominent thian in C^. tenuicornis Clans, This species is closely related to _C_. signatus Koch, from which, however, it differs in the character of the antennal ridge, the absence of the fine teeth of the eighth, ninth, tenth, twelfth, thirteenth, and fourteenth segments of the antemiae, and in the presence of a sense club. It differs from C_. tenuicornis in not being so coarse in any of its details, in tiie ciiaractef of the an tennal ridge, in the different proportions of the last antennal joints, and in the lesser width of the second and third cephalotho- racic segments. Cyclops viridis Fischer. (PI, IX., Fig. 54.) 1820. Mono cuius quadricornis viridis , Jurine , ( 1) ,p. 4fi, ])1.IIT. ,fig.l. Cyclops viridis , Fischer , (2) , p. 412, pi. IX., figs. 1—11. " brevicornis, Claus, (5) ,pl.TII. ,f igs.l2— 17. " gigas , Brady, (R), p. 105, pi. XX. " ingens, Herrick(lO), p. 228, pi. IV., figs. 1—8. 1851. 1857. 1878. 1882. 1885. 1884. 1886. u Viridis, Cragin,(ll), p.S, pi. IV. , figs. 8 — 16 n Herrick, (12) , p. 145. Vosseler, (15) , p. 190, pi. IV. 1886. 1891. Underwood, ( 14) , p. 552, Brady, (17), p. 17, pi. V., figs. 6— 10 A widely distributed sj^ecies, witli stout, sliort, 17-jointed 50 antennae, reac^ling barely to the end of the first cepiialo thoracic segment. Total length l.S mm. Longest seta. 5 mm.; fiirca .1 mm. Cephalotliorax just twice as long as the abdomen. Specim.ens foimd at Qjiincy varied somewhat, reaching nearly twice the above measure- ments, which rex)resent average specimens. Abdomen narrow, one fifth the width of the cepJrialothorax at its widest x)^rt; the last segment with serrulations. Basal segment of antennae longest, the sixth slightly longer than the third, tliirteentli and fourteenth of the same length as the eightli, twelfth a little longer, the last three somewhat longer still and not much attenuated, equaling the preceding five and a half segments. Setae all rather short or blunt, sense club show- ing plainly its setose origin by modification. Antennules mich de- veloped. Thoracic legs armed as follows: First Pair. Oiater ramus. Inner ramus. Kx., three spines, Ap.,two setae. In. , two setae. Ex. ,one seta. Ap.,one seta, one spine (large). In. jtliree setae. 51 Second Pair, Outer ramus. Ex., three spines. Ap. ,one spine, one seta. In., three setae. Inner ramis. Kx. ,one seta. Ap.,one seta, one spine, In., three setae. Third Pair. Armed like tlte second, Fou3:i:h Pair. Outer ramus. Ex . , tliree spines , Ap., one spine, one seta. In. , three setae. Inner ramus. Ex. ,one seta. Ap.,two spines (outer the short- er) . In. , two setae. Feet of the fifth pair bi-articulate. Basal segment broad, in length abo\it half its width, with a long seta at its outer pro- duced angle; apical segment small, about as wide as long, with one long seta (six times as long as the segment and somewhat longer than the preceding seta| and a minute spine at the inner apical an- gle about lialf as long as the segment. This sx^ecies is well characterizes by its short, thick anten- nae, tiie last three segments of which never equal more than the pre ceding five and a half segments. Owing to the prominent cJiaracters of insectus and my sjiecies (5) , viridis is not easily confounded 82 with them, Cyclops sigmtus Koch. (PI. TII., Fig. 16.) ' 1820. Mono cuius quadricornis alhidus » Jurine,(l), p. 44, PI. II., figs. 1!D,11. 1857. Cyclops cororiHtus , Claus,(4), p. 29, pi. II., figs. 1—11. . " , Clfi\is,(5), p. 97, pi. II., fig. 16; pi. X.,fig. 1. clausii , Poggenpol, (6) , p. 70, pi. XV., figs. 4 — 14. 1865. 1874. 1878. 1885. 1886. 1891. signat\is , Brady, (8), p. 100, pi. XVII., figs. 4—12. " var. fasciacornis , Cragin,(ll), p. 5, pi. TI., figs. 1—14. • Vosseler, (15) , p. 189, pi. IV., figs. 1—5. ' Brady, (17), p. 6, pi. II., fig. 5. This species is closely related to gyrinus and tenuicomis , occupying a median position with regard to tliem, tenuicornis being the grosser in all its details. The most prominent chiaracteristics of signatus are the rows of the teeth on the distal borders of seg- ments eigiit, nine, ten, twelve, thirteen, and fourteen of the first antennae. (PI. III., Fig. 16.) Circlet of hairs on basal antennal joint small, faintly per- ceptible; serrated ridge on last segment coarser than in gyrinus , and serrate on the proximal half of the segment, instead of the dis tal as in g yrinus . No sense club on twelfth segment. Like tenui- cornis , tliis species has the three transverse rows of minute spin- ules on eitlier side of the fifth thoracic segment. Antennules 7>Z With third segment twice as long as the second, which is three fourths as wide as long. This is one of the most widely distributed species of the ge- nus in Europe- Found by me only in collections made from Cedar Lake, in nortliem Illinois, under the direction of Professor S. A. Forbes, of the Illinois State Laboratory of Natural History. Cyclops tenuicornis Claus. (PI. HI., Figs. 17, 18.) 1820. Mono cuius quadricomis fuscus, Jurine,(l), p. 47, pi. III., figs. 2—4. 1857. Cyclops tenuicornis, Claus, (R), p-^^l, pi- III., figs. 1 — 11- 1865. " ■ Claus, (5), p. 99, pi. I., fig. 5 pl.II. ,fig.l7;pl, IV. fig. 5. 1875. 1878. 188S. 1884. 1886^ 1886. 1891. clausii , Poggenpol, ( 6) , p-70, pi. XV. , figs. 4—11. tenuicornis , Brady, (8), p. 102, pi. XVIII., figs. 1—10. " Cragin,(ll), p.?i, pi. ,11 . ,f igs. 1—14. " Herrick, (12) ,p.l02,pl.R. ,f ig. 17. • Vosseler, (15) , p. 189, pi. IV., figs. 6 — 10. ■ Underwood, (14) , p. 551.' signatus, Brady, (17) , p. 6, pi. II., fig. 5. First cephalo thoracic segment narrow anteriorly, and nearly twice as wide posteriorly; in length equal to the three following 54 segments and abdomen, exclusive of caudal rami. Gross in all its details, but resembling gyrinus and signatus in armatures of tho- racic legs and the three transverse rows of fine spinules on the fifth body segment (Fig. 17). Circlet of hairs on basal joint of antennae prominent. The last three gintennal segments much elongated, with ^^ridge, not ser- rate nor as prominent as in either gyrinus or signatus. A promi- nent sense seta on the twelfth segment. The second and third seg- ments of the antennules are almost equal in length, or nearly half as wide as long- Abundant in England, and Kurope generally ; found by cragin at Cambridge, Massachusetts; and by me in a collection received from Mr, Chas. C. Adams, of Bloomington, Illinois. Cyclops thomasi Forbes. (PI. ^IX. ,Figs . 55,56.) 1882. Cyclops thomasi , Forbes , (9) , p. 649, pi. IX., figs. 10, 11 — 16. 1882. " • Cragin, (11), p. 68, pi. III., figs. 1—15. 1884 " ■ Herrick, (12) , p. 151, pl.U. , figs. 5, 7, 8. 1886. " • Underwood, (14) , p. 552. 1887. " ■ Forbes, (16), p. 707, pi. II., fig. 8. 1891. " " Brady, (17), p. 15, pi. VI., figs. 1—4 1891. " ■ Forbes, (18), p. 249, pis. XXXIX. , XL. A widely distributed species, for full description of which see Forbes, (18), p. 249. r ^5 Cyclops phaleratus Koch. (PI. IX., Figs. 61 — 04.) 1851. Cyclop s canthocarpoldes Fischer, (2) , p. 426, pi. X. , ^ figs. 24, 25, <^2— 38. 1857. " • Clans, (5), p. 57, pi. I., figs. 6—10. 1863. " ■ Clans, (5), p. 102, pi. IV., figs. 1—4. 1878. " " Brady, (8), p. 105, pi. XX. 1882. ■ adolescens , Herrick , ( 10 ) , p. 231, pi. VI., figs. 16—20. 1885. " perarmatus , Cragin,(ll), p. 7, pi. I. figs. 9—18. 1884. " phaleratus, Herrick ,( 12) , p. 161, pi. P., figs. 6 — 10. 1886. ' ■ Underwood, (14) , p. 331. 1891. " ■ Brady, (17), p. 25. A medium-sized species, with the first cepiialothoracic seg- ment broad, and equaling the four and a half segments following. Length, exclusive of ca\idal setae, 1.3 mm. Antennae 11-segmented, reaching to the middle of the first cep}ialo thoracic segment, the basal joint equaling the next two seg- ments, the tliird as long as the fourth and fifth, the fifth half the length of the sixth, the eighth, ninth, and tenth somewhat oval in outline, the eleventh narrow, bearing one very prominent seta (about thiree times the length of the segment) and four or five smalL or ones. Labnan eigiit- toothed. Apical segment of the legs of the first pair somewhat longer than broad, bearing apically two setae, the outer simll, slender. \ 4 56 spine-like, three spines without and three setae within. Besides j the usual armature, there is a fringe of spinules along the outer edge of each ramus. Apical segment of the imier ramus with one stout spine and two lar^e setae at tip, a row of small spinules, and one seta without and two setae within. A somewhat remarkable lobe- like process at the inner base of the inner ramus, the inner edge setose, the outer somewhat thickened, crest-like. The second and third pairs of feet agree with the first, ex- cept tJriat the apical segment of the inner ramus has one extra seta within, and that the apical spine of the outer ramus is large. Ai)ical segment of the outer ramus of the fourth pair bears one spine and two setae at tip, two spi^ies and a few small spinules without, and two setae within. Apical segment of the inner ramais tipped with one remarkably long spine, and another about half as 'j long; one seta and a row of small si)inules without, and two setae within. Feet of the fifth pair mere simple flange-like processes bear- ing three subequal spines, the outer of which is roughly plumose, ^ its inner, plain (Fig, 61), A ridge of tooth-like processes extends from side to side, uniting the feet. Abdomen fully half as wide as long, tapering gradually, the last segment about a third the length of the preceding, with a row a? of large spiniiles posteriorly. Rami of the same proportions, as long as the last two abdominal segments, armed with small spiniiles besides the usual caudal setae. The inner terminal caudal seta very short and slender; the outer spine-like, about the same length I as the ramus; the second from within fully twice the length of the abdomen, plain at the baseband more sparsely spino-plumose on its inner than outer edge; the third from within one third the length of the second, spinose on the outer, cilio-spinose on the inner, edge. This sx^ecies was found only in shallow water among ruslies and lily pads in the soiithwest cove of Cedar Lake, in northern Illinois. Cyclops serrulatus Fisclier. (PI. IX., Figs. 57, 58; PI. III., Fig. 14 1851. Cyclops serrulatus , Fischer, (2) , p. 425, pi. X., figs. 22, 23, 26 — 31. 1857. " • Claus,(3), p. 36, figs. 1—3. 1863. " • Claus,(4), p. 101, pi. T., figs. 1, 2; pl.IV. ,fig.l2;pl.XI.fig3. 1878. " 1 Brady, (8), p. 109, pi. XXTI., || figs. 1—14. 1883. " pectinifer, Cragin,{ll), p. 6, pi. IV., figs. 1—7. 1884. ■ serrulatus , Herrick, (12) , p. 157, pi, 0., figs. 17—19. 1886. " agilis, Vosseler, (13) , p. 190, pi. V.,figs. 29—31. 1886. " serrulatus , Underwood, ( 14) , p. 331. 1891. " " Brady, (17), p. 18, pi. VII., fig. 1- f 58 Body slender, antennae 12-jointed, reaching to the middle of the third cephalothoracic segment; the last three joints very long and narrow. The form described hy Cragin as C. pectinif er found, but s\ich a variable proportion of caudal setae obtain, that I consider it less a sx)ecific ciiaracter tirxan a mere variation of serrulatus , A- waiting, therefore, further developments, I have classed C. pectlni f er Cragin under sermlatus . Feet of the fifth P'air consist of but a single joint, lobed or produced at the tip, and bearing one large spine and two setae. Everywliere common in Europe and the United States. Cyclops capilliferus Forbes. (PI. X.,Figs. 65-^69.) 1891. Cyclops capilliferus , Forbes, (18), p. 248, pi. XL., figs. 14—17. A 16- jointed sx^ecies, examined by me simply for comparison, and as yet only known to occur in Grebe Lake , Yellowstone National Park- FAiMTLY CALANIDAE. Djaptomus sicilis Forbes. (PI. VIII., Fig. 45.) 1882, Diaptomus sicilis , Forbes, (9), p. 541 — 645. 1884. " pallidus var. sicilis , Herrick, (12) ,p.l57. 1B8B. ■ sicilis. Underwood, (14) , p. 529. 59 1887. Diaptomus slcilis , Forbes, (16), p. 702, pi. I.,Fig.6. 1891. " " Forbes, (18), index. Found abundant in every locality indicated in the table of distribution"'*; it is notably a fresh-water species. A closely similar form was commonly found with it, which is probably the variety imperfectus . Dlaptomus oregrpnensis Lillj. (PI. VIII., Fig. 47.) 1889, Diaptomus oregonensis, de Guerne ^ Richard, ( 16) , px). 5S,54,pl.II. ,f ig.5;pl.TT^ fig. 8. Collected only in Cedar Lake, in northern Illinois, where numbers were found with a few specimens of _D. sicilis . Diaptomus sanguineus Forbes. (PI. IX., Figs. 59, 60.) 1876. Diaptomus sanguineus , Forbes, (7), p. 15, figs. 24, 28—50. 1882. " ■ Forbes, (9), p. 647, pi. VIII., figs. 1—7, 15. 1884. ■ ■ Herrick, (12) , p. 158, pl.Q,. , fig. 12. 1889. ■ ■ de Guerne ^ Riclaard , ( 16) ,pp. 20,21, pl-IV. ,f ig. 24, A medium-sized species, common to ponds throughout central Il- linois; quite abundant in pond collections made at Normal and Ur- bana, Illinois. ^See p. 48. 40 Diaptomus stagnalis Forbes. (PI. XI., Fig. 75.) 1882. Diaptomus stagnalis, Forbes , (9) , p. 645, pi. VIII., figs. B, 10—12, 14. 1882. ■ giganteus , Herrick , ( 10) , p. 1884. ■ stagnalis , Herrick, ( 12) , p. 139, pl.O.. , figs. 11 — IB. 1886. ' ■ Underwood, (14) , p. 529. 1889 ' " de Guerne Richard, ( 16) , p. 25, pi. IV., figs. 14—16. With the exception of Dj shoshone this is the largest Diapto TTTiis known to me . Atnmdant in collections made in April from pond south of Ur- bana, Illinois. Diaptomus si lo shone Forbes. (PI. VIII., Figs. 52, 55. )k 1891. riai)tomus shoshone , Forbes, (18), p. 251, pi. XLII., figs. 25 — 25. distinguished by its large size, and as yet found only in Ijake Shoshone and adjacent lakes and pools of Yellowstone National Park. Diaptomus lintoni Forbes. (PI. VIII., Figs. 50, 51.) 1891. Diaptomus lintoni , Forbes, (18), p. 252, pi. XLII., figs. 26—28. Closely related to D^, stagnalis , but smaller and with larger antennae . Like the previous species, lintoni has as yet been found 41 only in lakes and pools of Yellowstone Park. Osphranti 013171 lab rone c tun Forbes. (PI. VITI., Fig. 44.) 1882. Osphranticiira lab rone ctiim , Forbes, (9), p. 645, pi. VIII., figs. 24—28, 29; pi. IX. , figs. 1,2,4, v5, 7, 9. 1^84. * " Herrick, (12) ,pp.l54,155, pi. Q,. , figs. 1 — 8. 1886. " " Underwood, (14) , p. 529. 1889. ' " de Guerne <^ Richard, ( 16) , p. 97, pi. IV., figs. 1,2., Found by me in collections made by Professor Forbes from yionds near Clifton, 111., and in collections made by Mr. H. S. Erode from a ditch along the Havana branch of the Illinois Central Railroad near White Heath, Illinois, May IS, 1895. Kiuschura lacustris Forbes. (PI. VIII., Figs. 48,49.) 1882. Kpischura lacustris , Forbes, (9), pp. 541, 648, pi. VIII. , figs. 15, 16, 21, 25, 25, 27; pi. IX., fig. 8. 1884. ■ " Herrick, (12) , p. 151, pi. Q. , fig. 15. 1886. ■ " Underwood, (14) , p. 529. 1889. ' ' de Guerne ^ Rici\ard, ( 16) , p. 90, pl. VII., figs. 5,9,10. This si)ecies seems to have ciuite a wide distribution in the larger lakes of Illinois and Wisconsin, as may be seen by refer- ence to my table of distribution on another page. 42 FAMILY HARPACTIDAK. CanthocamptuR illinoisensis Forbes. (PI. VTTT., Fig. 46; PI. XI., Figs. 70—72.) 1876, Cant ho camp tus illinoisensis , Forbes , ( 7) ,p. 14, figs. 25,26,27,31. 18B4. " ■ Herrick, (12) , p. 170, pi. Q,. , figs. 1 — 5. 1886. • ■ Underwood, (14) , p. 552. A small robust species, averaging 1.'^ mm. in length- Antennae of female 8-segmented, as long as the fused first and second cephalothoracic segments; process on the fourth segment bearing a sense club about as long as tlie following two segments, and three setae somewlxat longer; tlie fifth segment the shortest, obliquely united to the preceding; the last segment somewlv\t longer than either the sixth or seventh, with a constriction near the end ca\ising an appearance of segmentation; sixth segment bearing two setae near tlie middle of the segment. Antennules with five long setae at tip, three of which are prehensile on account of cross articulations; tlie outer, longest, bristle with two short spinules on the bristle itself, near its middle. Flagellum on the middle of the basal joint, narrow, with two bristles at tip and two on its inner side. Last tl^ree thoracic segments eciualing the first two fused, the I 45 posterior one the shortest. Segmentation line between the first and second abdominal segments indistinct, the two segments not quite as long as the following two, which are equal, and each near- ly twice as long as the posterior segment. Each abdominal segment with two rows of coarse spinules sliglitly anterior to the sutures, the next to the last segment mich produced over the last. Caudal rami triangular to oval i7~ shape, as wide as long, and two thirds the length of the preceding segment. Of tlie two termin- al setae the inner is fully as long as the abdomen, sparsely spi- no-plumose; the outer slender, lialf the length of the preceding, bare on tiie inner side, sparsely spino-plumose on tlie outer. Be- sides these there is a tuft of three short spines and one seta, three or four times as long, at the inner terminal angle y and two setae as long as the preceding seta, and two or three sliort spines, on tiie outer margin. Legs of the first pair with both rami three- jointed, the in- ner ramus much elongated, its basal joint almost as long as the out- er ramus, the second joint about half the length of the apical, which is scarcely lialf the length of the basal and very narrow; the apical segrient tipped in botii sexes with three setae, the out- er leaving the character of a spine, the middle the longer, the in- ner as short as tlie segment, both tlie latter prehensile. Segments 44 of the outer ramus not much longer than broad, the apical segment with two spines and two prehensile setae at tip. Besides the above armatures, all the leg segments bear small spinules, the number varying. Legs of the second and third pairs differ in the same indi- vidual and in the sexes. Inner ramus of second pair of legs of fe- male three-jointed, nearly the same length as the o\iter, while in males the inner ramus is only half the length of the outer , but has the same number of segments. Legs of the third pair, in males, with the inner ramus short, the basal and second segments almost aborted, the second segment with two prominent setae within, the ap. ical sub-oval in outline, and about as long as the corresponding segment of the outer rairnis. Legs of the fourth pair not differing mtuch in the sexes, the inner ramiis two-jointed, half the length of the outer, the basal joint about a third the length of the apical, which is as long as the middle joint of tlie outer ramus, and has three setae within and one seta and one spine at the tip. Rudimentary legs of the male smaller than those of the female, of two joints, the inner being but a plate-like process, in length to width as one to three, bearing three spines at tip, of which the inner is two and a half times the length of the segment, the others 45 shorter, the outer about as long as the segment. Outer joint short, almost oval, three spines at tip, the inner about as long as the ramus, while the middle one is stout and twice as long, one spine and three or more spinules without. Basal joint of the rudimentary legs in the female broad, the outer basal part produced, bearing the second joint, in width to length as three to five, having apically six large plumose setae, of wliich the inner, or longer, just equals the joint in length. Second joint smaller, two thirds as long as the preceding, half as wide, oval, with two plumose setae at tip, one short bristle with- in and two without, and niunbers of smaller spinules on each margin. II Common in Y)onds of central Illinois, and also found in a col- lection made from a small creek running into Lake Winnebago, Wis- consin, south of Oshkosh, by Professor Forbes and party of assist- ants under the auspices of the United States Fish Commission, J\ine, 1892. BiBlIOGRAPHICAL INDKX. The following list comprises the published works referred to by me in the preparation of this paper. 1. 1820. JIJRINK, L.,Histoire des Monocles qui se trouvent aux environs de Geneve. 46 2. i851-5P>. FISCHER, S. , Beitrage zur Kenntniss der in der Umgegend von St . Petersburg sich findenden Cy- olopiden (und Fortsetzung) . (Bull. Soc. imp. Moscou. 1851. 1855.) 3. 1857. CLAUS, C. , Das Genus Cyclops und seine einheim- ischen Arten. (Wiegrnann • s Archiv, 1857.) 4. 1857. CLAUS, c. , Weitere Mittheilungen fiber die ein- heimischen Cyclox)iden. (Ibid.) 5. 1865. CLAUS, C. , Die frei lebenden Cox)epoden mit beson- derer weriicksicht igung der Fauna deutschlands , der Nordsee und des Mittelmeeres. jj 6. 1874. POGCtENPOL, M. J., List of the Copepoda, Cladocera, and Ostracoda of the environs of Moscow.* 7. 1876. FURBES, S. A., List of tiie Illinois Cnistacea. Bull. 111. State Lab. Nat. Hist .Vol. T , ,No. 1.) 8. 1878. BRADY, G. S. , A Monograph of the free and semi- parasitic Copepoda of the British Islands. Vol. I. (Ray society.U 9. 1882. FORBES, S. A., On some Entomostraca of Lake Mich- igan and adjacent waters. (American Natural- ist, Vol. XVI.) • 10. 1882. HERRTCK, C. L., Cyclopidae of Minnesota, with Notes on otl\er Copepoda. (Tenth Ann, Rep. Geol. and Nat, Hist. Surv. of Minn.) 11. 1885. CRAGIN, F, W, , A Contribution to the History of the Fresh-water Copepoda. (Trans, Kansas Acad. Sci, Vol, VIII.) 12. 1884. HERRICK, C. L, , A Final Report on the Crustacea included in the orders Cladocera and Copepoda. ^Ll2tli Ann, Rep. Geol. and Nat. Hist, Surv. Minn.) ^1 liave iiad access only to tjie translations of tiie descriptions of Cycloi)S contained in this Memoir, as given by Prof. Cragin in Vol. VI TI. (1883) Trans. Kan. Acad. Sci. 47 15. 1886. VOSSKLKR, J., Die freilebenden Copepoden ^"urtten- "bergs und angrenzender Oegenden. (Inaugiiral- ■pi ssertation der hohen Tiaturwissenschiaf tlichen Fakiiltat der Universitat Ti'ibingen. ) 14. 1886. WKRWOOD, LUCIKN M. , List of the described spe- cies of Kresh-water Crustacea from America, north of Mexico. (Bull. 111. State Lab. Nat. Hist. Vol. II. , Art . V. ) 15- 1887. FORBES, S. A., On some Lake Superior Kntomostraca, (Ann. Rep. U. S. Comra. of Fish and Fisheries for 1887. ) 16. 1889. DK GIJERNE, J., et RICHARD, J., Revision des Cala- nides d'eau douce. (Memoires de la Socifet6 Z»-| ologique de France, Tome II.) 17. 1891. BRADY, G. S. , A Revision of the British species of Fresh-water Cyclopidae and Calanidae. (Nat. Hist! Trans. Northumberland, Durham, and Newcastle- upon Tyne, Vol. XT., Pt.l.) 18. 1895. FORBES, S. A., A Preliminary Report on the Aquat- ic Invertebrate Fauna of the Yellowstone Na- tional Park, V/yoming, and of tlie FlatJiead Re- gion of Montana. (Bull. TI. S. Fish Comra.1891.) TABLE OF GEOGRAPHIC DISTRIBUTION. Qjiincy , Chicago Br'kwater, Me re do s ia^^ Fox Lake. Peoria Lake. Pekin. Bloomington. No rmal . Beaver Dam Lake._ Champa i gn , _Clifton. ^lougii Pond, JWhite HeatJ-i. Lake Zurich. Sand Lake. J^ourth Ji!^ke._ /ISCONSIN.^ Lake Winne ba go. " Geneva. De la van. Mich igan. n X X X X z z z r-\ Oi rH Wl m to 03 -H 05 0) (D 0) (U CO -H •H -H -H -H d Ti O C O O E H w •H to o X / / X X X X M O to r-l o •p ft •H tiD 5b bD O O to to 0) o — * CO o to z / X X / CO •H (0 Id) (0 c rH •H to ft e c o (SJ I ^ • Q) « c •H O CO o c to ^ •H ft ft K K O X X 4^ H H etf S o u to c: o •H -P O CD H rH O O n c •H i X to 0) •H o 0) ft to c •H O to 0) •H •H c5 u O X Mendo ta, X IMINNESOTA. INDIANA Pine Lake. Doming. L , Mi nne t o nka^ Bass Lake. Calhoun Lake. X / Harriet Lake, Grebe Lake. Yel lowstone Lake. Heart Lake. z / ZZ Xi X Z X Twin Lake. Mary Lake. Flathead River. Goose Lake. !x X x / x X X X *0f tiie signs used in this table the abundant , X= conmon, and few. I 49 ARTIFICIAL KEY TO THK FAlvlILIES OF THE FREE-LIVING COPEPODA.^ Order COPEPODA. Body witiiout bivalve carapace, first antemae connonly largest. Eye single and simi)le, or rarely paired and comYiound, in parasitic forms sometimes wanting. Thorax anr) abdomen commonly well distin- guished, Cnist not iiardened, usually delicate and transparent. Four or five pairs thoracic legs (rarely wanting) ,t]iese 2-branched, flattened for swimming, but without branchial appendages, a. Females with one egg sac. b- Males with but one antenna (tlie right, seldom tlie left). With hinge joint. Body elongate, abdomen much narrow- er tiian tliorax; first antennae long, normally 24- or 25-jointed, second antennae large, commonly two- branciied, accessory branch large, mandibular palpus us- ually two-branched, maxillipeds large and long, with marginal bristles. Five pairs of develop.ed legs, "^^The key to tlie families is copied from that used in the zo- ological laboratory of the University of Illinois. 50 all 2-b ranched, vrith {5- jointed outer "branches except tlie fifth pair, wliich are often not V) ranched, and greatly modified in both male and female, hut especial- ly in tlie former, where they are commonly unlike on the two sides and form sexiial grasping organs. (CALANIDAE.> Furca with but tliree large terminal bristles to each branch. Abdomen of the male unsymmetrical , provided with lateral preliensile apparatus; fifth pair of legs of tlie female not branched, 5- Jointed, not ter- minating with a long spine. Fpischura . Furca with four large terminal bristles to each branch. d. The inner brancii of tiie first pair of legs 2- jointed, the corresponding V- ranch of the three otlier pairs 5- jointed. Fifth pair -of legs of male and female 2-b ranched, internal branch rudimentary. Diaptomus . dd. Both internal and external branches of all the first four pairs of legs R-jointed. Fiftli pair of legs of both sexes 2-branched, those of the female only differing from the other legs 51 by Yiresence of a, strong interml liook at tiie second joint of the outer branch, tiiose of tlie male witli tl^e irjier branch 8-jointed j and provided with i>liimose iairs, as in the otiier legs. e. Fiftli pair of legs of the female with the inner l^airs of tlie last joint of the out- er branch transformed into short thick jj spines. Fiftli pair of legs of the male witli two joints to the outer branch of the left leg and three to the outer branch of the right. Qsphrantician , ee. Fifth pair of legs of tlie female with the internal liairs of the last joint of the outer branch long and plumose- Fifth pair Of legs- of the male witli two joints to both outer branches. Limnocalanus , bb. Both antennae of males with hinge- joint. Body cylindric-' ai, abdomen but little narrower tlian tliorax and not sharply distinguished froTiiit; antennae short, " ' jointed, scarcely longer tlian first somite, first four , I pairs of legs two-branched, fifth pair foliaceous; simi- 1 52 lar in the sexes, first pair usually unlike the others, and prehensile (Harpactidae) , second antennae witli devel- oped accessory branch, body linear; first pair of legs prehensile and different from the others, both branches 8-jointed; mandibular palpus simple, 2- jointed, last max- illiped slender. Canthocamptus . aa. Females witli two eg^^ sacs. Males with first antennae botli pre- iiensile, second antennae never prehensile, simple, 4- jointed, palpus of mandible and of maxilla rudimentary; fifth pair of legs rudimentary, alike in the sexes (Cyclopidae) . Mandibular palpus in form of small tubercle , bearing two long bristles , tho- rax oval or ovate, much broader thian abdomen, composed in malej of ten segrients, in female of nine. Cyclops. ARTIFICIAL ANALYSIS OF THE SPECIES OF CYCLOPS JIRNTIONED IN THE PRESENT PAPER. a. Legs of the fifth pair with tliree spines or setae on tlie apical segment; 1 — 2 segmented, b. Legs of the fifth pair 2-segmented. c. Furcal bristles all developed (longer tlifin the furca). Antennae 17-jointed, reaching nearly to the fourtii cephalothoracic segment. A circlet of hairs on 55 tlie basal anteniial segment. d- No sense club on the 12th antennal joint. 10, (e) Antennal segments 8,9,^12,15,14 each provid- ed with a crown of coarse serrations. The third segment of the antennules long. gignatus (p. 52). dd. A sense club on the 12th antennal joint. f . Distal antennal segment withi a narrow plain ridge. Tiiirrl joint of t]ie antennules equal to the second joint. Circlet of hairs coarse. Tenuicornis 'p. 55). ff . Distal antennal segment with a broad finely serrate ridge. Circlet of liairs sparse. ^ Gyrinus (p. 28). bb. Legs of the fifth pair not segmented. (Pepresented only by a narrow plate-like process and tliree bristles in Plialeratus . p . 55 ) . g. Only the tvro middle furcal bristles developed. The inner and ou.ter sliorter than the furca. h. Antennae 12-segmented and as long as tlie cephalo-( tiiorax; the last four segments attenuated. 54 i. Fiircal rami slender, tiie outer nargins with a row of spinnles. ^ ■' ;■ '"^ ^ j. The second fiiroal bristle from withoiit more tlv=in lialf as long as the third. Sermlatus (p. ^7). aa- Legs of the fifth pair segmented, tJie ai)ical segment always with two siiorter or longer bristles, k. Both end-bristles of tlie same length; at least one ai^prox- imately lialf tiie length of tlie other. 1. Fiircal bristles all developed; at least tlie inner longer than the fiirca. m. Anteniiae 17-segraented, siiort,er tlian the cepiialo- thorax, with ridge on the last segment. No circlet of hairs on tlie basal segrient. n. Ridge witli a semilunar notcli or hook. No sense cl\ib on 12th segment. Uv . Cycloxjs sp, ( 5 ) ( p . 21 ) . nn. Ridge with several hook-like notches. A flense club on 12th segment. Edax (p. 25). mm. Antennae 16- jointed. No ridge; no circlet of iiairs. Capilliferus (p. 58). 55 11. Only the two mldrlle f ureal bristles develoi)ed; the inner and outer shorter tl\an tlie furca. o. Antennae 17-jointed, shorter tlian ti.e cephalotho- rax. No ridge; no circlet of hairs, p. Antennae not longer tlian the first cephalo- thoracic segment. Cyclops sp.(4)(p.l9) pp. Antennae reaching to the tiard cepiialotho- racic segment. Cyclops sp. (2) (p,i3) , ppp. Antennae reaching nearly to tiie (fourth) cephalothoracic segiient. Rami with small patch of point-like teeth on their upper third. Thomasi (p.;54) . kk. One end-bristle reduced to a short rudiment. o^. Furcal bristles all developed; at least the inner the same length as tlie fu.rca or longer, r. Antennae 17-segmeiited, shorter than the cephalo-f.i ii i thorax. A sense club on tlie 12tli segment. : s. Tlie last three antennal segments eojialing the preceding five and a half, Viridis (p. 29). sa. The last three antennal segments equaling 56 the seven and a half preceding ones, Cyclops sp. (5 ) ( p . 16 ) . qq. Only the two middle fiircal bristles developed; the in- ner and outer shorter than the furca. t. Antennae 17-jointed. A sense club on the 12th segrient. No circlet of hairs; no ridge, u. Antennae as long as the first cephalothorac-i ic segment. Insectus (p. 26). uu. Antennae shorter tlian the first ce].hialotho- ic segment. (The outer furcal bristle knife-like, resembling a spine.) Cyclo]^s sp. (1) (p.lO) . 57 EXPLANATION OF PLATES. P 1 t e I. Figs. 1 — 6. Cyclops (1) . (1) Adiat female. (2) Antenm of fe- male- (5) Labnun. (4) Fiftii leg. (5) First leg. (6) Fourth leg. Plate II. Figs. 7 — 12. Cyclops (2) . (7) Adult female. (9) Labnun. (10) Fifth leg. (11) First leg. (12) Fourth leg. Plate III. Fig. 15. Cyclops (^), fourth legs. Fig. 14. Cyclops serrulatus, fifth leg. Fig. 15. Cyclops edax, terminal segments of antenna of female. Fig. 16. Cyclops signatus, antenna of female. Figs. 17 — IB. Cyclops tenuicornis . (17) Fifth leg. (18) Antenna of female. Fig. 19. Cyclops gyrinus, first legs. 58 Plate IV. Figs. 20—24. Cyclops (4) , (20) Adult female. (21) Fifth leg. (22) Antenna of female. (2r>) First leg. (24) Fourtli leg. P 1 a t e V. Figs. 25--50. Cyclops (5). (25) Adult female. (26) Antenna of fe- male. (27) Terminal segments of antenna. (28) Fifth leg. (29) First leg. (oO) Fourth leg. Plate VI. Figs. 61 — 56. Cyclops edax. (51) Adult female. (52) Labrum. (58) Antenna of female. (54) Fifth leg. (55) Fourth leg. (56) First leg. Plate VII. Figs. 57—42. Cyclops insectus . (57) Adult female. (58) Anterjia of female. (59) Labrum. (40) Fiftli leg. (41) Fourtli leg. (42) First leg. 59 Plate VIII. Fig. 45. CyclopK gj^rinus, antenna of female. Fig. 44. sphrant i CI in labronectiun, fiftli legs of female. Fig. 45, Diaptomus sicilis, fiftli pair of legs of male. Fig. 46. Canthocarnptiis illinoisensis , fiftli leg of female. Fig. 47. lUaptomus oregonensis, fiftli pair of legs of male. Figs. 4B, 49. Kpiscinira lacustris. (48) Fifth leg of female. (49) Abdomen of male. Figs. 50, 51. Diaptomus lintoni . (50) Fifth leg of female. (51) Fiftli pair of legs of male. Figs. 5?., 55. Diaptomus shoshone. (52) Fifth leg of female. (55) Fifth pair of legs of male. Plate IX. Fig. 54. Cyclops viridis, fifth leg. Figs. 55 » 56. Cyclops thomasi. (55) Rami. (56) Fifth leg. Figs. 57, 58. Cyclops sernilatus . (57) Rami of typical specimen. (58) Rami of variety x>ectinifer (?). Figs. 59. 60. Diaptomus sanguineus. (59) Fifth leg of female. (60) Fifth pair of legs of male. 60 Figs. 61 — 64. Cyclops phaleratus. (61) Fiftli leg. (62) Antenna of feiriHle. (65) First leg. (64) Fourth leg. Plate X. Figs. 65 — 69. Cyclops capillifenis. (65) Adult female. (66) An- tenna of female. (67) Fifth leg. (68) First leg. (69) Fourth leg. Plate XI. Figs. 70 — 72. Cantliocamptus illinoisensis . (70) First leg of male. (71) Antenna of femfile. (72) Fifth leg of male. V Vhl^ IV V \ V r Plate VIII t