ERRATA. Page 12, lines 16 and 17, for one hundred read three hundred and for one thousand read six hundred. Page 17, line 2, dele first letter in the line. Page 168, line 12, page 177, lines 13 and 14, and page 271, line 10, for Lemna tnsulca read Spirodela polyrMza. Page 209, line 2 of foot-note, after hut insert represents. Page 2;'56, line 7, and page 266, line 19: snoioi n. s. has been shown to be hieroghjijhka, (^. Page 257, insert as line 8 as follows: -ken to the office produced young in ten days. The Page 272, line 13, for P. higuUatus read Pompiliis higuttatus. Page 278, Plate Y., 16, after view insert as follows: a, mentum; 6, labial rudiment; c, maxillary palpi; d, maxilla; e, labrum; /, antenna; g, eye; h, mandible. Page 286, line 11, drop initial the one line. Page 386, line 1, for Comstocki read Comstock. Page 399, line 17, for specimens read specimen. Page 411, line 10, for Michaelson read Michaelsen. Page 441, line 3 from bottom, for 66 read 68. Page 445, line 10 from bottom, for 57 read 5S. Page 466, line 1 from bottom, for Cyima read Oypris. Article XV.— Contribution to a Knowledge of the Worth American Fresh-water Ostracoda included in the Fami- lies Cytheridce and Cyprididm. By Richard W.Sharpe, B. S. INTRODUCTION. The present paper has been prepared in the course of work at the University of Illinois for the degree of master of science in zoology. In addition to extensive collections of Entomostraca made at the Biological Station of the University of Illinois, situated at Havana, on the Illinois River, I have been able, through the kind- ness of Dr. S. A. Forbes, to examine all the accumula- tions in this group made by the Illinois State Labora- tory of Natural History during the last twenty years, and covering a territory little less than continental. The greater part of the material studied is from the rivers, ponds, and lakes of Illinois and immediately ad- jacent states, but at least a cursory examination has also been made of collections from the Yellowstone National Park and from the lakes of northwestern Montana. Although the Ostracoda of Europe have now been ex- tensively studied, but little work has been done upon this order in America. Prof. C. H. Turner, of Clark University, Atlanta, Ga., has, however, paved the way for American students in this field (35, 62, 63, and 64), and scattered descriptions occur in the writings of some others. The earlier practice of distinguishing species by characters derived from the shell alone has had the effect to surround the study of this group with extraordinary difficulties and greatly to complicate the synonymy. More recentlv Tnueli rise has been ma'lo of the structure of North Amei'ican Fresh-water Ostracoda. 415 the soft parts of these Crustacea, with the result to add several new genera, mostly described by Prof. G. 0. Sars. For the convenience of students who follow me I have tliouo-ht it best to embody synopses of all these genera in the text. Of the twenty-two species herein mentioned fourteen are new to America, and twelve I believe to be un- described. Two of these species belong to the genus Limnicythere and to the family CytheridtB, itself new to America. It is a pleasure to me to say that whatever value this work may have is due in great part to the kind encouragement I have received from Dr. Forbes, and to his generosity in providing both material and Uterature foi- my use. LIFE HISTORY AND HABITS.* Unlike the other groups of Entomostraca, most of which, independent of shores or bottom, swim easily and continuously throughout the waters they inhabit, the Ostracoda commonly occupy a more restricted range in small and shallow waters, or along the bottoms and margins of large lakes and streams. With them, the act of swimming is more laborious because of the structure of the animal and the weight of the shell. In collections of the limnetic plankton, therefore, they are either want- ing, or present only in relatively insignificant numbers. In consequence of the temporary nature of the small bodies of water in which they are usually found, they are much more frequently observed during the spring- months. At this time, in a little short-lived wayside pool or ditch vast numbers may make their appearance, soon to disappear with the drying up of the water. They may also be seen in such situations in the fall. They thrive in both clear and turbid waters, either in the midst of aquatic vegetation or on a bare mud bottom. Most of * The text and tables under this head were prer-ared by Mr. C. A. Hart. 4:16 Illinois /State Laboratory of Natural History. them are scavengers, though some species feed upon min- ute aquatic vegetation, such as diatoms and filamentous Algae. Ten of the species and both of the families herein treated were represented in collections of the Biological Station from the region covered by its operations in the vicinity of Havana. The collections examined were partly surface, bottom, and oblique tows taken with a fine tow- ing net in the deeper and more open waters, and partly catches with the towing net or Birge net from among the vegetation along the gently-sloping shores. In the first table following, the distribution of each species is shown with regard to the various collecting sub- stations, which are grouped according to their general character. Full descriptions of these localities may be found in a previous article of this volume.* The total number of collections examined from each substation is given immediately beneath the letter designating the sub- station. The lower, larger number of each pair in the table indicates the relative abundance of the species, on the scale of 5, 1 meaning rare, and 5, excessively abundant. The smaller numbers above these show the number of collections in which the species appeared. It will be seen that in the off-shore collections the first three genera (Limnicythere, Cyprinotus, and Candona) do not appear at all, while the last two (C^^pria and Cypridopsis) appear a number of times. This indicates a difference in habits, and does in fact correspond to a decided difference in structure. The members of the second group possess well-developed swimming hairs or natatory setae, and appear not only in the bottom tows but in the surface tows also, even in the river channel at station E. * Article VI.. p. 151. North Amenncom Fresh-water Ostracoda 417 ~ 8 "fe. s ^^ ^ 418 Illinois State Lahoratory of Natural History. ^ JSorth American Fresh-water Ostracoda. 410 In the second table, the same data are grouped with regard to the time of year, the figures having the same meaning as in the preceding table. The rise in abund- ance in spring is quite evident, and probably would be more so if the earlier months were better represented. The first three genera (Limnicythere, Cyprinotus, and Candona) are absent during the summer months, reap- pearing in fall in lesser numbers. The remaining species (Cypria and Cypridopsis) are more uniformly distributed thi-ough the year. As they seem more at home in larger bodies of water, while those of the preceding group are accustomed to live in small ponds and streams which often dry up in midsummer, this difference would natur- ally be expected. A fall list of the species treated in the following pages^ accompanied by biological data, is next given for com- parison. Unless otherwise specified, the data given are from the records and collections of the State Laboratory. The relative abundance is indicated by a figure, as in the preceding tables. The entire absence of species of Cypris from the Biolog- ical Station list is doubtless due to their occurrence in small ponds in preference to larger bodies of water, such as the lakes and streams of the Havana region. Family Cytheridce. Limnicythere reticulata n. sp. Pond, Urbana, April, (2). illinoisensis n. sp. Lake shore, Havana, May, (1). These species are evidently crawlers or burrowers rather than swimmers. Family Cyprididce. Oyclocypris forhesi n. sp. Pond, Bloomington, April. CypriTiotiis pellucida n. sp. In water from creek, Urbana, April; roadside pool, Havana, Sept., (4) ; creek near Quincy. lu?iingtonensis Turner. Jan. and March (Turner); Nor- mal, May. incongruens Ramd, Abundant in pools in spring (Vavra): Pt. Pinellas, Fla., May. 4-20 Illinois State Lahm^atory of Natural History. Cypris reticulata Zadd. Ponds, Normal, Feb., (2), and April, (5); Cypress swamp, Ky., Sept., (1). fuscata Jurine. Pond, Urbana, April, testudinaria n. sp. Pond in woods, Bloomington, April. Candona acuminata Fischer. Pond, Clifton, May, (2). recticauda n. sp. Pond, Clifton, Feb. simpsoni n. sp. Lake and river shores, Havana, April, (4), May, (3), Oct., (1), and Nov., (1); pond, Urbana, April, (3). falmformis Fischer. Abundant in March and April in small pools (Vavra); pools, Normal, March; August (Turner). sigmoides, n. sp. Lake and river shores, Havana, May, (2), and Oct., (1). reflexa n. sp. Lake shore, Havana, April, .May, and Nov., (1). Cypria pustulosa n. sp. Bottom tows in river channel, surface and bottom tows in lakes, and lake and river shores, Havana, May, (2), July, (1), Aug., (1), and Sept., (2). ohesa n. sp. Lake shore, Havana, May, (3). dentifera n. sp. Zoological Gardens, Cincinnati, 0., Aug. exsculpta Fischer. Common in most running streams. Bottom tow in river channel, lake and river shores, Havana, April, (1), May, (3), July, (2), and Oct., (1); ponds, Chfton, Feb. and May, (3); Normal, May; shore of L, Minnetonka, July, (1); Fourth Lake, Aug., (1). ophthahnica Jurine. Surface and bottom tows in river channel, (2), surface and bottom tows in lakes, and lake and river shores, Havana, Feb., (l),Apr., (1), May, (3), June, (2), July, (1), Aug., (3), Sept., (2), and Oct., (1). A scavenger and act- ive swimmer (Vavra). Common in ponds and ditches where there is little or no vegetation (Brady). Pools, Normal, March, (4); shore of L. Minnetonka, July, (1). North American Fresh-ioater Ostracoda. 421 Oypridopsis vidua O. F. Miiller. This cosmopolite seems to occur quite uniformly in all kinds of waters and at all seasons. smaragdina Ydvra. Ditch entering Calumet R., Aug., (2); found in July and August (Yavra). SYNOPSIS OF FAMILIES TREATED IN THIS PAPER.* 1 (4). Second antennae simple, subpediform, geniculate, clawed at the apex, not very unlike the upper an- tennae; both pairs of antennae bearing long setae and adapted for swimming, or shortly setose and not used for swimming. Mandibles distinct, mostly strongly toothed at the lower extremity; palp of mod- erate size, bearing a more or less developed branchial appendage. First pair of maxillae bearing a large branchial plate, ^[osth' fresh-water forms. Trihe PoDOCOPA. 2 (3). Three nearly similar pairs of feet, all directed downwards and used for locomotion. Caudal rami obsolete, forming two rounded setiferous lobes. Antennae very little adapted for swimming. Cytheiiid.1i;. 3 (2). Two dissimilar pairs of feet; the anterior pair ambulatory, the posterior pair not used for locomo- tion, bent backwards within the valves. Caudal rami commonly well developed, mobile, and bearing two terminal claws. Antennae commonly with natatory setae. Cypridid.e. 4 (1). Second antennae two-branched; one branch rudi- mentary, immobile, the other elongate, flexible, with long natatory setae (Myodocopa); or both branches well developed, movable, and natatory' (Cladocopa); or both branches flattened, similar to the feet of the Copepoda (Platycopa). Marine tribes. * Modification of a key prepared by Brady (6). 422 Illinois State Laboratory of Natural History. Family CYTHERID^. "Shell mostly hard, calcareous, usually with an un- even surface either sparingly clothed with hairs or alto- gether bare; hinge generally toothed. Eyes more or less separated, sometimes wanting. Antennules sub- pediform, geniculate at the base; five- to seven-segmented; beset with short setae which are partly spine like. Anten- nae strong, pediform, curved, four- or five-segmented, with two terminal claws; basal segment bearing a long seti- form biarticulate flagellum, which conveys a duct from a poison gland; second segment destitute of a setose brush. "Mandibles usually strong, enlarged and toothed at the apex; palp well developed, directed forward, and bearing on the posterior margin strong curved setae and a poorly developed branchial appendage. First pair of postoral appendages more or less maxilliform; the three following alike, pediform, directed downwards, adapted for walking. One pair of branchial laminae attached to the maxillae. Caudal rami obsolete, form- ing two rounded setiferous lobes. Copulatory organs of the male large and complex; in addition to which there is a curious bifurcate appendage between the feet of the first pair; ovaria and testes not produced between the valves; no mucous gland. Animal incapable of swim- ming."—G. 0. Sars. I am not aware that representatives of this family have heretofore been reported for America. Of the dozen or more genera belonging to this family, but one (Limni- cythere) seems to be purely a fresh-w^ater genus. I. Ijimnicythere Beady. 1850. Cythere, Baird (2, p. 163). 1868. Limnicythere, Brady (6, p. 419). 1878. Acanthopus, Vernet (72, p. 516). 1888. Limnocythere, Dahl (20, p. 615). 1889. Limnicythere, Brady & Norman (9, p. lYO). 1891. Limnicythere, Vdvra (68, p. 107). North American Fresh-ioater Ostracoda. 423 Shell strong, irregularly tuberculate or spinous, rather thin and horny in texture; extremities yellowish or hyaline. The first pair of antennse five-segmented, provided with short bristles on their outer edge ; second pair four- segmented, the "spinning claw" being either two-seg- mented or unsegniented. The branchial plate of the mandible strongly developed (commonly rudimentary in other genera of this group). Caudal rami rudimentary',, commonly but two short bristles. Males are rare. Previous to Vavra's monograph (68) but five species wei"e known: L. sancti-patricii B. & R. ; L. ri'umstrifica Norman, from England ; Z. inopinata Baird, from England and Sweden; Z. relicta Lillj., from Sweden; and Z. incisa Dahl, from Germany, Vdvra (68) adds Z, stationis as new, and Zschokke (76) has recently described L. neocomensis from Switzerland. I have found two species which presumably are not yet described. Limnicythere reticulata n. sp. (PI. XXXIX., Fig. 1-7.) A small form, .06 to .73 mm. in length, .35 mm. high, and .25 mm. broad; gra3isli white. Shell sparsely hairy at the anterior and posterior ends; conspic uously marked with a honeycomb-like network of polyg- onal reticulations (Fig, 1 and 2), which are somewhat similar to those of Z. sancti-patricii and L. illinoisensis, but with lateral furrows which serve at once to distin- guish it from these species. The upper anterior part, in the neighborhood of the eye, is nearly free from reticula- tions, marking the position of a lateral depression which is deepest near the middle of the shell, becoming shal- lower anteriorly. Seen from the side (Fig. 2), the shell is evenly and gradually rounded at both ends; dorsal margin straight, the ventral sinuate, the deepest part slightly anterior to the middle; posterior part somewhat broader than the anterior. 424: Illinois State Laboratory of Natural History. Seen from above, the shell is sharply and narrowly pointed anteriorly, broadening quickly and then sud- denly contracting to broaden again slightl^^ «o that it is widest back of the middle, from which it slopes grad- ually^ to the somewhat bluntly pointed posterior part. Seen ventrally (Fig. 1), the lateral depressions show to greater advantage, appearing as two constrictions; one just posterior to the middle, the other considerably an- terior to it. Muscle impressions (Fig. 2) four, elongate-oval, situ- a-ted at the bottom of a circular lateral depression, their longest axes parallel to that of the shell and to one another. As with L. neocomensis and L. statlonis, the first an- tennce (Fig. 5) have a long, narrow terminal seg- ment about seven times as long as wide, armed api- cally with three equal setae, one of which is cleft apically for about a third of its length, having the appearance of a "sense seta," the inner branch being about half the length of the outer. In other respects the antennae are the same as in other described species. The second antennae seem armed in no especial way. The three terminal spines are strong, plain, and much curved, the two longer being equal in length and four times the length of the apical segment; the other, seta- like, and about an eighth shorter. "Urticating setae" two-segmented, reaching to the middle of the terminal spines. All of the inner setae blunt and spine-like. The palp of the mandible is short and plump. Maxillae not especially armed in any way; outer edge of the base smooth. The first of the three pairs of feet is the shortest, the others increasing in length in regular order backwards. All are armed similarly, with a few slight exceptions. The terminal claw of the first foot is slightly longer than the last two segments taken together; the spine- like seta on the inner apical edge of the second segment North American Fresh-water Ostracoda. 425 is two fifths loDf^-er than the third segment; third and fourth segments of equal length. Terminal claw of third pair as long as the united lengths of the last three and a half segments (Fig. 6); antepenultimate seg- ment as long as the last two segments, the spine-like seta on its inner distal edge of the same length ; width of basal segment one fourth its total length; two spine- like setae on its lower inner edge, the distal seta twice the length of the other. Rudimentary caudal rami (Fig. 3) cylindrical, thick, blunt, about three times as long as wide, with a small seta near base, not over two thirds as long as the width of the ramus, and a stouter one near the tip of the ramus, twice as long as the preceding one. The posterior dorsal part of the carapace (Fig. 7) tapers to a spine-like point, and upon the dorsal aspect there are several rows of tooth-like notches. Described from several specimens taken from a smalt pond (Hedges' Pond) south of Urbana, 111., April 10, 1896. A number were raised from mud taken from the bed of the pond. Limnicytliere illmoisensis n. sp. (PI.XXXIX., Fig. 8- 13; and PL XL.) A medium-sized species, .88 mm. long, .40 mm. high^ and .29 mrn. wide; dark grayish white. A few scatter- ing hairs on the surface of the shell, which is rather inconspicuously marked on its entire surface with polyg- onal areas, which are, however, very faint compared with those of L. reticulata. With a high power these areas are found to be filled with small elongate-oval to quadrangular granules (PI. XXXIX., Fig. 9). Seen from the side (PI. XXXIX., Fig. 8), the shell i& evenly and gradually rounded at both ends, the dorsal margin straight, the ventral deeply sinuate, the deepest part at the anterior third, just below the muscle im- pressions. (In L. reticulata the deepest part is just pos- 42 G lUuiois State Laboratory of Natural History. terior to a vertical line passing throuo'h the muscle im- pressions.) The posterior part is considerably broader than the anterior. Seen from above, the shell is sharply and concavely pointed anteriorly, then quickly broadens and remains of the same width nearly' to the posterior end, which is convexly and bluntly pointed. There is a constriction or sinus (PI. XXXIX., Fig. 13) just in front of the middle, which, in the position indicated in Fig. 1, PI. XL., is seen to be double. The deeper sinus is just anterior to the middle and above the muscle impres- sions. Anterior to this is a small conical elevation separating it from another smaller sinus or constriction from which the surface slopes quite quickly to the ante- rior part. The radiating hairs of the anterior and posterior parts are more abundant than in L. reticulata, and resemble those of L. neocoinensis. The anterior hyaline flange is three times as wide as the posterior one. (PI.'XXXIX., Fig. 8.) Muscle impressions four, elongate-oval, situated at the bottom of a circular depression just anterior to the mid- dle of the shell and just above the deepest part of the ventral sinus, their long axes parallel to that of the shell. There are two or three similar depressions in the same vicinit3^ Terminal segment of the first antennae (PI. XL., Fig. 6) four times (in female) or five times (in male) as long as wide, armed apically wir^h three setae, the terminal one of which is divided apically as a "sense seta" and is once and two thirds the length of the segment ; the other two equal, and one fourth longer than the segment. The penultimate segment is a fourth longer than the last one, while the antepenultimate is but half as long as the penul- timate. The one preceding this, and also the basal seg- ment, are ciliated along their inner edges (PI. XL., Fig. 6). The second antenna of the male differs from that of North American Fresh-water Ostracoda. 427 the female in that the terminal claw is armed with three or four strong teeth at tip (PI. XL., Fig. 5). The basal part of the penultimate segment has two cir- cles of hairs, as has also the antepenultimate segment, which is two sevenths the length of the penultimate. "Urticating seta" two-segmented, reaching to the middle of the terminal spine; all the inner seti^ blunt and spine- like, as in L. reticvlata. Maxillae and mandibles not especially different from those of other members of the genus. Feet of first pair (PI. XXXIX., Fig. 11) shortest, armed like those of the second. Basal segment of second pair faintly ciliated exteriorly near the base; penultimate segment slightly longer than the last, both together equaling the antepenultimate; terminal claw nearly equal to three preceding segments, and in male with two or three accessory teeth near the tip (PI. XL., Fig. 3). Feet of third pair (PI. XL., Fig. 4) in the male with an unusuall^^ long terminal seta,—as long as the united segments of the foot,—faintly cross-striated on its distal half, its place of attachment surrounded by a circle of cilia, as is also the joint between the last and penultimate segments; the last two segments together equal to the antepenultimate, which has on its inner dis- tal edge a plumose seta as long as the segment; basai seg- ment somewhat triangular in shape, three times as long- as wide. Rudimentary caudal rami (PI. XXXIX., Fig. 12) cy- lindrical, six to seven times as long as wide, gradually tapering to a seta-like extremity which is five sevenths as long as the main part of the ramus. Two dorsal setae: one situated about the width of ramus from base and as long as the width of the ramus; the other just anterior to the seta-like termination, and about the same length as the first. The male sexual grasping oigans are ^unusually well developed and as shown in PI. XL., Fio:. 2. 428 Illinois State Laboratory of Natural History. Described from specimens found at the Biological Sta- tion in a shore collection made at Thompson's Lake (Station G), Havana, 111., May 2G, 1895. Family CYPRIDIDiE. "Shell g, p. 116, Taf. XI., Fig. 8-14). 1868. Cypns tessellat'i, Brady (6, p. 366, PI. XXIII., Fig. 39-45). 1883. Cypris affinis, Lilljeborg (41, p. 146). 1889. Cypris reticulata, Brady & Norman (9, p. 76, PI. VIII., Fig. 1-2; XII., Fig. 5-7). 1891. Cypris reticulata, Ydvra (68, p. 99, Fig. 34J-342). 1893. Cypns reticulata, Daday (19, p. 296). Length 1.25 mm., height .72 mm., width .62 mm. Shell translucent to clear yellowish, with a dark blue patch dorsally and just posterior to the eye-spot. The strikingly sculptured form of the shell (Fig. 3) is es- pecially noticeable in the young stages. This sculpturing resembles striations at the center of the shell, changing to radialh^ arranged patterns resembling filagree work. Occasionally, in old specimens, this characteristic surface- marking may be almost absent, but a collection could hardly be made which did not contain some specimens showing it clearly. Seen from the side, the shell is much the broadest in front, highest at the anterior third, where there is a small gibbous elevation, below which is the eye-spot. The dorsal margin slopes rapidly back to the quite nar- row posterior extremity; ventral margin nearly straight, slightly sinuate just posterior to the middle. Seen from above, the shell is tumid, oval, widest in the middle, and tapering somewhat more rapidly an- teriorly. The dark dorsal coloration appears in the form of a rough cross. The longest of the natatory setse reach but slightly beyond the terminal claws. The first pair of maxillae are slender, weakly developed the spines on its first process toothed in ray specimens, which differ in this particular from Vavra's, in which these spines are described (66, p. 100) as smooth. Second foot long, slender, the terminal claw covered, slender, and twice as long as the terminal segment. 442 Illinois State Laboratori/ of Natural Hidory. Caudal rami (Fi<^. 4) straight, weakly bent near the end, from ten to twelve times as long as wide, and very fainth' toothed on the dorsal margin. Terminal claw slender, straight, finely tooihed at its extremity, and nearly three fifths as long as the ramus; subterminal claw five sevenths as long as the terminal claw, straight. Terminal seta slender, short, of the same length as the dorsal one, which is one third the length of the sub- terminal claw and distant from it the width of the ramus. This species occurred in April, 1884, in great numbers in a small grassy pool on the grounds of the Normal University at Normal, 111. (Collection Illinois State Lab- oratory of Natural History). According to Brady it seems to make its home only in such pools, and is yet to be found in lakes or large bodies of water. The species is also known to occur in Great Britain, Sweden, Ger- many, and Russia. Cypris fuscata Jurine. (PI. XLIIL, Fig. 5.) 1820. Ifonocnlus fiiscatus, Jurine (36, p. 174, PI. XIX., Fig. 1, 2). 1837. Cyirris adusta, Koch (38, Heft. XI., p. 3, Fig. 3). 1838. Cypns galbinia, Koch (38, Heft. XXI., p. 19, Fig. 19). 1844. Cypris fuscata, Zaddach (74, p. 32). 1850. Cypris fusca, Baird (2, p. 154, Tab. XIX., Fig. 7). 1850. Candona hispida, Baird (2, p. 161, Tab. XIX., Fig. 4). 1853. Cypris fuscata, Lilljeborg (39, p. 114, Tab. X., Fig. 6-9; XII., Fig. 5). 1854. Cypris fuscata, Zenker (75, p. 73). 186S. Cypris fusca, Brady (6, p. 362, PI. XXIII., Fig. 10-15). 1887. Cypris dugesi, Herrick (34, p. 26, PI. IV., Fig. 7). 1888. Cypris fusca, Sostaric (60, p. 47). 1889. Cyprisfuscata, Brady & Norman (9, p. 73, PI. XII., Fig. 3, 4). 1891. Cypris fuscata, Vavra (68, p. 98, Fig. 33^ -33^ ). 1893. Cypris fuscata, Daday (19, p. 292). 1894. Cypris fuscata, Turner (64, p. 16, PI. VIII., Fig. 41-46. 1895. Cypns /M,scato, Turner (35, p. 320, PI. LXXI., Fig. 41-46; LXXII., Fig. 7, 7p; LXXVL, Fig. 9). Length 1.46 mm., height .82 mm., width .76 mm. Color yellowish brown with a bluish black patch on *^ither side near tlie middle and just posterior to a North American Fresh-ionter Ostracoda. 443 vertical line passiiioj through the eye-spot. The anterior part also is tipped with a dark patch. The form and intensity of coloration of these patches seem to be va- riable, but in general they are as described above. The surface of the shell is quite rough, as though covered with a loose scaly epithelium, and rather thickly set with short hairs. Seen from the side, the shell is oblong-ovate, highest at its anterior third, sloping rather quickly to the posterior extremity, which is somewhat narrower than the anterior. Seen from above, the shell is elongate-oval, the ante- rior end somewhat more acutely pointed than the pos- terior; widest at the middle. Maxilla stout, the spines on its first process toothed. Terminal segment of second foot one thirteenth as long as the penultimate segment, which is seven ninths as long as the preceding one. Terminal claw much bent and twice as long as the terminal segment. Caudal rami (Fig. 5) long, slender, straight, more than twenty times as long as wide, the dorsal edge finely toothed. Terminal claw slightly bent, slender, finely toothed, and one half as long as the ramus; sub- terminal claw two thirds the length of the terminal one, straight, finely toothed near the tip. Terminal seta slender, about half as long as terminal claw, and twice as long as the dorsal seta, which is one and a half times width of ramus from the subterminal claw. The specimens studied by me were obtained from a pond south of Urbana, 111., April 16, 1892, and are now in the collection of the Illinois State Laboratory of Nat- ural History. The species occurs in Great Britain, Germany, and Sweden; and, in America, in Mexico and New Mexico (Herrick), at Cincinnati, Ohio (Turner), and at Urbana, 111. (Coll. 111. State Lab. Nat. Hist.). 44-4 Illinois State Ijohoratory of Natural Ilistoi^. Cypris testudinaria n. sp. (PI. XLIV., Fig. 1-4.) This species is 1.15 mm. long, .74 mm. high, and .65 mm. wide. Shell very thin, dirty brown to.ochreous, and in all the specimens seen of a leathery flexible con- sistency, as if composed mostly of animal matter. Indeed^ the shell might be rolled like parchment—a peculiarity not known to me as belonging to any other species of Ustracoda. It is rather thickly covered with short hairs, and there is also a thick marginal row. Seen from the side, the shell is rather narrower an- teriorly than posteriorly, elongate-elliptical in outline, the ventral margin somewhat straighter than the dorsal. Natatory setce of the second antennae (Fig. 4) short, simple, just reaching the tips of the termi- nal claws. The terminal claws are straight, moder- ately stout, hooked at tips, finely toothed, and as long as the last three segments. Terminal segment twice as long as wide, one fifth as long as the penultimate, which is seven eighths as long as the antepenultimate; ante- penultimate segment a little more than three and a half times as long as wide, the sense club short, nearly straight, situated just below the middle of the segment. There is a crown of cilia at the base of the natatory setse, extending to the inner apical edge of the segment. The spines of the first process of the second maxillae- are toothed. Claw of first foot (Fig. 2) bent, rather stout, lightly toothed, and one sixth longer than the last three segments combined. The last segment is as wide as long, the outer of the two terminal setae being twice as long as the segment. The fourth segment from the last commonly has a crowm of setae near its base, besides scattered marginal ones. Terminal claw of second foot about a third the length of the terminal segment, which is one seventh as long as the penultimate segment. The reflexed seta of the terminal segment is half the length of the penulti- mate seo-ment. Nmth Aine)*ican Fresh-water Ostracoda. 445 Caudal rami (Fig. 1) slender, slightly bent, the dorsal edge serrate for two thirds its length, sixteen to eighteen times as long as wide. Terminal claw nearly straight, lightly toothed, half as long as the ramus. Terminal seta half as long as the terminal claw, which is one and a third times as long as the subterminal one; dorsal seta two thirds the length of terminal one, and width of ramus from subterminal claw. The "organ of Zenker" presents an unusually spiny appearance (Fig. 3), since the spines are thickly set over the entire surface of the cylinder instead of being in wreaths, as is commonly the case; organ fully five times as long as wide. Described from a number of specimens in the collection of the Illinois State Laboratory of Natural History, which were taken from a pond in the woods near Bloom- ington, 111., April 22, 1879. V. CYPRICERCU3 SaeS. 1895. CypHcercus, Sars (58 p. 37). Natatory setae of both pairs of antennre well developed ; palp and masticatory lobe of the first maxillse narrow. Feet as in the genus Oypris. Caudal rami excessiveh' developed and elongate, afford- ing a ready means of recognition. Coecal appendage of intestine unusually short; ovarial tubes much elongated. This genus has but recently been established by Sars (57) to receive a South African form with excessively de- veloped caudal rami. No species have been reported as yet from America. YI. Erpetocypris Brady & Norman. 1792. Cypris, O. F. Miiller (49, p. 48). 1820. MonoiilKS, Jurine (36, p. 170). 1889. Er; etocypris, Brady & Norman (9, p. 8^;. Second pair of antennip five-segmented. Natatory setae of the third segment very short, not nearly reaching the tips of the terminal claws and not plumose. Having no 446 Illinois State Laboratory of Natural History. power of swimming", the animal creeps along the bot- tom—a very different habit from that of Cypris. Twelve species are known, two of which were described from America. An anal^^tical table of the species occurring or likely to occur in this country is inserted here for the convenience of workers. I have examined none but E. harhatus (Forbes). KEY TO SPECIES OF ERPETOCYPRIS. 1 (7). Caudal rami with two terminal claws and a ter- minal and dorsal seta. 2 (3, 6). Claw on last segment of second foot as long as segment. Shell about twice as long as high. Caudal rami about ten times as long as wide, dorsal margin finely toothed; dorsal seta not more than once width of ramus from subterminal claw. E. STRiGATA (0. F. Miiller). 3 (2, 6). Claw on last segment of second foot three times as long as last segment. 4 (5). Dorsal seta of caudal ramus delicate, undevel- oped, close to subterminal claw; dorsal edge of ramus armed with five combs of teeth; terminal seta fully as long as subterminal claw. Shell somewhat longer than twice its height, the upper and lower edges nearly parallel. E. reptans (Baird). 5 (4). Dorsal seta of caudal ramus transformed into a short spine or claw, close beside the subterminal claw ; dorsal edge of ramus armed with an unbroken row of fine teeth ; terminal seta three fourths as long- as the subterminal claw. Shell seven thirteenths as high as long, the upper edge evenly convex, the under edge very weakly concave. E. oLivACEA Brady & Norman. 6 (2, 3). Claw on last segment of second foot seven , eighths as long as last segment. Dorsal seta serrate and claw-like, close to subterminal claw ; dorsal edge of ramus finely toothed; ramus twenty times as long as wide; terminal seta about a third as long North American Freial flange; right valve with a row of tubercles anteriorly and ventrally. C. pustulosa n. sp. 3 (2). Terminal setse of second feet approximately as long as the terminal segment. 4 (5). Terminal claw of caudal i-amus half the length of the ramus. C. ophthal.mica (Jurine). 5 (4). Terminal claw of caudal ramus three fifths the length of the ramus. 6 (7). Dorsal seta of caudal ramus rudimentary, shorter than width of ramus, situated at four times the width of the ramus from the subtermiual claw, and above the center; subterminal claw with a comb of very long teeth beyond the center of the claw. C. DENTIFERA U. Sp. 7 (6). Dorsal seta slender, two and a half times as long as ramus is wide, and two and a half times width of ramus from subterminal claw, which is almost smooth. Shell marked with closely set parallel and anastomosing lines. C. exsculfta (S. Fischer). 8 (1). Terminal seta; of second feet plainly unequal, th& shorter terminal seta being scarcely longer than the segment and but half the length of the other simi- larly directed seta. Dorsal seta of ramus three times width of ramus from subterminal claw. C. OBESA n. sp> North AmtTt'can Fresh-icater Ostracoda. 461 Cypria pustulosa n. sp. (PL XLVIII., Fig. 6-10.) This species is .51 mm. long, .39 mm. liigli at the highest part, and .22 mm. wide; clear brownish in color, with a dark patch anteriorly, another just above and posterior to the eye-spot, and still another on the posterior part. Both extremities are hairy, the disc moderately so. Lucid spots (Fig. 6) six, four large and two small, the smaller ones situated ventrally. All are elongate and situated near the center of the shell. Seen from the side (Fig. 7), the whole specimen seems to be highly arched, owing to the presence of a doi'sal flange on the left valve, ^vhich is otherwise of the form of the right. Right valve (Fig. 6) regularly arched dorsally; both extremities fully rounded, the anterior sloping, however, somewhat more rapidly ; ventral mar- gin nearly straight, except a small sinuation at the middle. Anterior margin of right valve (Fig. 6) with a row of thirteen to sixteen small tubercles, and just pos- terior to the ventral sinuation are three or four others, which are not so conical but seemingly flattened out and pointed posteriorh^ The sense club on the third segment of the second an- tennfB reaches but to the upper quarter of the segment, the terminal part being bent outwardly; natatory setae three times as long as the distance between their place of insertion and the tip of the claws; terminal segment twice as long as broad. Palp of first maxilla very prominently developed, the first segment twice as long as broad, the terminal seg- ment nearly circular, with two well-developed setse and three or four shorter ones. Terminal claw of first pair of feet (Fig. 8) smooth and as long as the tw^o segments preceding the last; the segment preceding these two hairy. Terminal segment of second foot (Fig. 10) small, carry- ing two equal, simple, distally directed setse and a re- flexed one, which is as long as the last three segments; ])enultimate segment provided with a row of cilia at its 462 Illinois State Laboratory of Natural History. distal end and several irregulai'ly scattered plumose cilia on its inner edge, also with a stiff seta on its inner edge situated slightly below the middle and reaching to the distal end of the segment; antepenultimate segment as long as the penultimate, covered with scattered plumose cilia and bearing a seta at its inner distal angle which is slightly longer than the seta on the penultimate seg- ment. Caudal rami rather long and narrow (Fig. 9), nearly straight, two and two fifths times as long as the ter- minal claw, which is weakly bent and smooth; subter- minal claw four fifths as long as the terminal one, pro- vided with a comb of long teeth near the tip. Terminal seta two fifths as long as the terminal claw ; dorsal seta situated at the middle of the ramus, scarcely as long as the ramus is wide. This Cypria occurs quite abundantly in the collections of the Biological Station, made near Havana, Illinois. Cypria obesa n. sp. (PI. XLYIII., Fig. 1-5.) Length .78 mm., height .48 mm., width .33 mm. Shell plump, clear to brownish yellow, with a few scat- tered elevations on its surface, but not especially marked in any way. Muscle impressions quite small. Seen from the side, the shell is of a regular suboval form with a straight ventral edge, three fifths as high as long. Second antennae of male six-segmented; terminal seg- ment twice as long as wide ; inner terminal claw half the length of the outer; apical part of fourth segment with two "sense setee" reaching to the tip of the terminal seg- ment; sense club on the inner edge of the third seg- ment rather short, extending slightly beyond the upper quarter of the segment; natatory setse only twice as long as the distance between their place of insertion and tips of terminal claws. Palp of right maxilla of male (Fig. 5) larger than that of the left maxilla (Fig. 4), and formed as shown in the figure. North American Fres/i^ioater Ostracoda. 403 Claw of last segment of first pair of feet (Fig. 1) smooth and slightly longer than the united lengths of the last three segments; terminal segment conical, about as long as wide; two segments preceding just equaling one another; seta at inner distal angle of antepenultimate segment as long as the penultimate segment. Last segment of second foot (Fig. 3) seven tenths as wide as long and a fourth as long as the preceding seg- ment; shorter backwardly directed seta half as long as the longer one, or just equal to the last segment in length ; antepenultimate segment slightly shorter than the penultimate, the seta at its inner distal angle as long as that on the penultimate segment. The anterior distal part of the penultimate segment has a crown of cilia surrounding a short seta, and there are also sev- eral clusters of coarse cilia on this and the antepenulti- mate segments. Caudal rami (Fig. 2) bent, somewhat stout, and nine times as long as wide, finely toothed along the inner margin. Claws evenly bent, finely toothed, but more coarsely so at middle; terminal claw three fifths as long- as the ramus; subterminal one half as long as ramus. Terminal seta of ramus three sevenths as long as the subterminal claw ; dorsal seta two thirds as long as the terminal one and situated three times the width of the ramus from the subterminal claw, or slightly beyond middle of ramus. Described from a number of male and female speci- mens taken at Havana, 111., August. 1895. Cypria dentifera, n. sp. (PI. XLVII., Fig. 6-11.) Shell .61) mm. long, .38 mm. high, and .26 mm. wide. Entire surface smooth; sparsely hairy except at each end; brownish yellow, witli dark brown markings afs follows: an anterior, a ventral, and a dorso-ventral patch, and a vertical stripe dorsally just x>osterior to the eye-spot. Muscle impressions in the form of a rosette, closely clustered, six or seven in number (Fig. 6). 46-4 Illinois State Laboratory of Natural Hhtory. Seen from the side (Fig. 6), the shell is highest just posterior to the middle, quickly sloping posteriori}^ more gradually anteriorly. The anterior margin of the right valve projects as a hyaline flange, receiving as in a pocket the anterior margin of the left valve, which is armed with a row of eighteen to twenty tubercuhform teeth. Ventral margin slightly sinuate at middle, the an- terior and posterior parts sparsely hairy. Seen from above (Fig. 7), the shell is widest back of the middle, blunt and evenly rounded, sides nearly par- allel, then quickly narrowing anteriorly to a rather pointed end. Natatory setae of second antennae long, slightly plumose, three of them reaching the entire length of the antennae beyond the terminal claws. Terminal and penultimate segments in female three times as long as wide. Mandibles and maxillae not especially marked ; palp of left second maxilla of male as in Fig. 8. i*irst pair of feet (Fig. 9) rather stout; terminal claw smooth, much bent, and as long as the last three seg- ments; terminal segment subconical, a third as long as the penultimate, which is of the same length as the an- tepenultimate; latter with a few scattered setae dorsally, and a short, slender seta at the inner apical angle, two thirds as long as the segment. Two terminal setae of the second feet (Fig. 10) ap- proximately equal, as long as the last segment, faintly toothed ; terminal segment sinuate on its inner edge, two thirds as wide as long; penultimate segment three and three fourths times as long as the terminal one, four times as long as wide, the dorso-basal edge some- what crenulate, the inner finely ciliate, a plumose seta at its middle point and a comb of cilia at its inner apical angle; antepenultimate segment as long as the penultimate, finely' setose on its inner margin and with a rather stout plumose seta at its inner apical angle, as long as the seta on the penultimate segment. The- North American Freshrwater Ostracoda. 465 long seta of the terminal segment is as long as the last three segments. Caudal rami (Fig. 11) rather stout, about ten times as long as wide. Terminal claw stout, nearly smooth, curved beyond the middle, and three fifths as long as the ramus; subterminal claw two thirds as long as the terminal one, with a comb of remarkably long teeth near the tip. These teeth are longest distally, decreas- ing in length towards the base of the claw. Terminal caudal seta half as long as the subterminal claw; dorsal seta very slender, nearly four times width of ramus from subterminal claw, upwardly curved, not longer than ramus is wide, situated slightly above center of ramus. This Cypria would attract attention from the manner in which the right valve overlaps the left, and it might be taken for C. inequivalva Turner (63, p. 6) except for differences in the second feet, in the markings of the shell, in the caudal rami, and some others. Described from a number of specimens in the collection of the Illinois State Laboratory of Natural History, taken in the Zoological Gardens at Cincinnati, Ohio, Aug. 30, 1881 . Not as yet known from any other locality. Cypria exsculpta S. Fischer. (PI. XLYII., Fig. 4). 1853. Cy ris elejanula, Lilljeborg (39, p. 206). 1855. Cypris exsculpta, S. Fischer (24, p. 652. PI. XIX.. Fig. 36-38). 1864. Cypns striolata, Brady (4, p. 60, PL III., Fig. 12-17). 1868. Cypris striolata, Brady (6, p. 372, PI. XXIV., Fig. 6-10). 1880. Cypris gramdata, Robertson (55, p. 18). 1887. Cypris stri 'lata, Herrick (34. p. 29, PI. IV., Fig. 3). 1889. Cypria exsculpta, Brady & Norman (9, p. 68, PL XI., Fig. 1-4). 1894. Cypria exsculpta, Turner (64, p. 13, PL VII., Fig. 2-8). 1895. Cypria exsculpta. Turner (35, p. 305, PL LXX., Fig., 1-8; LXXII., Fig. 3). Length .58 mm., height .37 ram., width .25 mm. Shell thin; clear yellow to transparent. 30- 466 Illinois StaU Lahoratoi'i/ of Nataral History. Seen from the side, the shell is broadly subovate, high- est in the middle, but of about the same width for two thirds its length; dorsal margin strongly arched, the eye-spot anterior to the highest point. Seen from above, the shell is a narrow, much com- pressed ellipse. Terminal segment of second foot a fourth as long as the preceding segment. The two short terminal setae are of the same length as the segment, the longer one as long as the last three segments. Caudal rami short, stout, and muchcurvedr Terminal claw smooth, curved, and about half the length of ramus ; subterminal claw five sixths the length of the terminal one, smooth, curved, twice the length of the terminal seta; dorsal seta somewhat longer than the terminal seta and situated slightly beyond the middle of the ramus. This species may at once be recognized by the mesh- work of anastomosing parallel longitudinal lines over the entire surface of the shell (Fig. 4). These ma}^ com- monly be quite readily seen, thus settling its identity at once, as I am not aware of any other ostracode with shell markings of this character. This species is quite common in most running streams, and was one of the commonest forms seen in my ex- amination of the collections of the Illinois State Labora- tory of Natural History from various localities, and of the Illinois Biological Station at Havana, 111. Cypria ophthalinica Jurine. (PI. XLVII., Fig. 5.) 1820. Monoculus ophthalmicus, Jurine (36, p. 178, PI. XIX., Fig. 16, 17). 1835. Cypris compressa, Baird (1, p. 100, PI. III., Fig. 16). 1837. Cypris tenera, Koch (38, H. XII., p. 3, Fig. 3). 1838. Cypris punctata, Koch (38, H. XXI., p. 23, Fig. 23). 1850. Cypris compressa, Baird (2, p. 154, Taf. XIX., Fig. 14, 14a-c). 1851. Cypris elegantula, S.Fischer (23, p. 161, PI. X., Fig. 12-14). 1853. Cypris compressa, Lilljeborg (.39, p. 112, Tab. X.. Fig. 16-18). 1854. Cypria punctata, Zenlcer (75, p. 77, Taf. III., Fig. A). North American Fresh-wattr Ostracoda. 467 1868. Cijpris compressa, Brady (6, p. 372. PI. XXIV., Fig. 1-5; XXXVL, Fig. 6). 1868. Cypris ovum, Fric & Nekut (27, p. 48, Fig. 30). 3872. Cypris ovum, Fric. (26, p. 228, Fig. 28). 1874. Cypris compressa, Brady, Crosskey, & Robertson (14, p. 123; PL I., Fig. 5, 6). 1885. Cypris punctata, Nordqvist (50, p. 150). 1888. Cypris ptmctata, Schwarz (59 p. 18). 1888. Cypris compressa, SostSLTic (GO, p. 47). 1889. Cypria ophthalinica, Brady & Norman (9, p. 69, PI. XI., Fig. 5-9). 1891. Cypria ophthalmica, Yavra (68, p. 63, Fig. 19i-19«, 201-20*). Length .56 mm., height .37 mm., width .32 mm. The American representative seems to be smaller than the European form, if one may judge from the descriptions of Yavra (68, p. 63) and of Brady (6, p. 372). . Shell much compressed, reniform, clear brown, except at the anterior and posterior ends and just back of the eye-spot where there are dark brown bands or patches, these three bands being perhaps a ready means of dis- tinguishing the species. Seen from the side, the dorsal margin is much arched, but hardly as much as in Vavra's specimens. Seen from above, the shell is widest at the posterior third, narrow, somewhat acutely pointed anteriorly and rounded posteriorly. Natatory setae very long, reaching beyond the tips of the terminal claws by more than the total length of the antennae, or three times as long as the distance between their point of insertion and the tips of the ter- minal claws. Terminal segment of second foot somewhat longer than broad, a third as long as the preceding segment, and sinuate at its inner margin. The two terminal short setae are about the same length and as long as the ter- minal .segment. Caudal rami (Fig. 5) short, rather stout, bent, and fully eight times as long as wide. Terminal claw simple, 468 Illinois State Laboratory of Natural History. curved, half as long as the ramus, subterminal claw two thirds as long as the terminal one, with a patch of teeth near its tip. Terminal seta half as long as sub- terminal claw ; dorsal seta slender, as long as width of ramus, situated at middle of ramus. The inner edge of the ramus was smooth in the specimens examined, thus differing from Vavra's description (68, p. 63). Minn., 1883 (Herrick); Baxley, Ga., 1895 (Turner); Havana, 111. (Coll. 111. State Lab. Nat. Hist.). Xin. Cypridopsis Brady. Cypri><, auctnrum. J820. JfonocK/it.s, Juriae (36). 1868. Cypridopsis, Brady (6, p. 375). Second pair of antennae five segmented. Natatory setae at end of third segment long and plumose. The branchia of the second maxilla consists of a plate bearing five plumose setae or else of two setae which are inserted di- rectly on the blade. Second foot five-segmented, with a strong chitinous claw at its extremity. Caudal rami rudimentary, flagelliform, base turgid, a short cilium on the dorsal edge. The males of this genus are unknown. There are eleven species, of which three are known to occur in America. KEY TO SPECIES OF CYPRIDOPSIS. 1 (2). Branchia of second maxilla with five setae. Three dark bands on dorsal and lateral aspect of shell; very plump. Common. C. VIDUA (0. F. Miiller). 2 (1). Branchia of second maxilla formed of two setae. 3 (4). Caudal rami cylindrical, turgid at base, suddenly narrowing to a bristle which is little longer than the basal part, C. NEWTONi Brady & Robertson. 4 (3). Caudal rami broad, gradually narrowing to a bristle. Shell much compressed. North Ame7'ican Fresh-water Ostracoda. 469 5 (0). Xatntory setae of second antennae reaching to the end of the terminal claws. Shell pale gT-eeu. C. viLLosA (Jurine). 6 (5). Natatory setae of second antennae reaching beyond the end of the terminal claws. Shell grass- green, at least dorsally. C. SMARAGDINA Vavra. Cypridopsis vidua (0. F. MtJLLER). 1792. ( ypHs vidua, O. F. Miiller, (40, p. 55, Tab. lY., Fig. 7-9). 1*20. Ilonoculus vidua, Jurine (36, p. 175, PI. XIX., Fig. 5, 6). 1837. Cyprismandata. Koch (38, H. X., p. 2, Fig. 2). 1841. Cyprisstriyata, Kocli (38, H. XXXVI., p. 19, Fig. 19). 1844. Cypris vidua, Zaddach (74, p. 35). 1850. Oypris vidua, Baird (2, p. 152, PI. XIX., Fig. 10, 11). 1850. Cypris sella, Baird (3, p. 158, PI. XIX., Fig. 5, 5a). 1851. Cypns vidua, S. Fischer (23, p. 162, PI. XI., Fig. 1-2). 1853. Cypris vidua, Lilljeborg (39, p. Ill, Tab. X., Fig. 10-12). 1854. Cypris vidua, Zenlier (75, p. 79). 1868. Cypridopsis vidua. Brad}' (6, p. 375, PI. XXIV., Fig. 27- 30, 46). 1868. Cypris vidua, Glaus (17, PI. I., Fig. 6-8). 1868. Cypris vidua, Frio & Nekut (27, p. 48, Fig. 29). 1869. Cypridopsis obesa, Brady & Robertson (10, p. 364, PI. XVIII., Fig. 5-7). 1870. Cypridopsis ohesa, Brady & Robertson (11, p. 15). 1871. Cypris vidua, Heller (31, p. 90). 1872. Cypris vidua, Fric (26, p. 227, Fig. 27). 1874. Cypridopsis obesa, Brady, Crosskey & Robertson (14, p. 128, PI. 1., Fig. 1-4). 1879. Cypri" vidua, nevTick (32, p. 112, PL XVII., Fig. 1). 1880. Cypridopsis vidua, Robertson (55, p. 20). 1887. Cypridopsis vidua, Herrick 34, p. 31, PI. IV., Fig. 1). 1888. Cypris vidua, Sostaric (60, p. 46). 1889. Cypridopsis vidua, Brady & Norman (9, p. 89). 1891. Cypridopsis vidua, Vavra (68, p. 75, Fig 23*-23*). 1892. Cypridopsis vidua, Turner (62, p. 73). 1893. Cypridopsis vidua, Daday (19, p. 300). 1894. Cypr dopsisv^dua. Turner (64, p. 19). 1895. Cypridopsis vidua. Turner (35, p. 312, PI. LXXII., Fig. 1-1;/: LXXV., Fig, 5, 6, 8, 9; LXXVI., Fig. 4, 7). This well known species needs no extended notice in this paper. 470 lU'uio'is State Laboratory of Natural History. Length, .60-.70 rara., height, .35 mm., width, .38- .45 mm. Seen from above, the shell is broadly ovate, widest back of the middle. Three characteristic darker bands varying from dark brown to green extend down each side from a longitudinal dorsal band. These bands to- gether with its oblong spheroidal form and plump appearance can hardly fail to identify the species. The caudal rami are rudimentary, the terminal part being produced into a long slender stylet which is some- what longer than the ramus. This species is ubiquitous, and I have yet to know of a pond or stream which it has not made its home. It is seemingly always present in aquaria, and appears to play the role of scavenger, thriving in situations to which other Ostracoda seem to be totally unadapted. Viewed with a low- power these creatures present a very pretty appearance as they rapidly swim about, the banded shell at once attracting attention. It would seem that its great adaptability to adverse situations and its scavenging habits might account in part for its almost universal distribution throughout the temperate zones. Cypridopsis smaragdina Vavra. (PI. XLVIII., Fig. 11-12.) 1891. Cypridopsis smaragdina, Ydvra (68, p. 80, Fig. 261-263). Length .65 mm., height .45 mm., and breadth .34 mm. This striking and interesting form appears at first glance, when seen from the side (Fig. 11), to be in the shape of a half-moon, except that the under edge is nearly straight. The shell is light to grass-green, es- pecially on its dorsal as^pect; alcoholic specimens, how- ever, commonly show but a trace of this coloration. Surface thickly covered with long hairs, which are all parallel to one another, backwardly directed, and closely appressed to the shell (Fig. 11). Xorth American Fresh-^cater Ostracoda. -471 The eye-spot, instead of being at the highest point of the shell, as in the typical forms described by Vavra, is slightly below and anterior to this location. The nata- tory set?e of the second antennae are long, reaching be- yond the tips of the terminal claws by the length of the claws, thus differing from C. vtllosa (Jurine), its near relative, the natatory setae of which reach but to the terminal claws. The caudal rami (Fig. 12) are rudimentary, the basal part c\'lindrical, more than three times as long as wide, then suddenly narrowing into a long flagellum, full^'" twice as long as the basal part. The ramus also has a dorsal seta at the termination of the basal part, slightly longer than the ramus is wide. South Chicago, August 24, 1881, from a ditch open- ing into the Calumet River (Coll. III. State Lab. Nat. Hist.). XIV. POTAMOCYPRiS BraDY. 1868. Bairdia, Brady (6, p. 474). 1870. Potamocijpris, Brady (7, p. 366). Second antennae four-segmented, third and fourth seg- ments bearing numerous setae, which are short, not reaching beyond the middle of the terminal claws; last segment with two strong terminal claws and two or three short, slender setae. Mandible stout, palp three- segmented and bearing a single branchial seta near the base. Feet as in Cypris, caudal rami rudimentary, con- sisting of a long seta with a lamellar base, bearing a short dorsal one commonly at base of the lamellar part. Shell compressed, outline when seen from the side sim- ilar to that of Cypridopsis. I know of but two species of this genus. — P. fulva (Brady) Si\i(\P. gregaria'^axH,—neither of which is known to occur in America. 472 Illinois State Lahoratory of Natural History. BIBLIOGRAPHY. 1. Baird, W., 1835—Trans. Berw. Nat. Club, Vol. I., p. 100. 2. 1850.—Natural History of the British Euto- iiiostraca. Printed for Kay Society. 36 plates. 3. 1859.—Proc. Zool. Soc. London. Plate. 4. Brady, G. S., 1864.—Species of Ostracoda New to Britain. Ann. and Mag. Nat. Hist., Ser. III., Vol. XIII., p. 59. 5. 1868.—On the Crustacean Fauna of the Salt Marshes of Northumberland and Durham. Nat. Hist. Trans. Northumberland and Durham, Vol. IIL, p. 1. 6. 1868.—A Monograph of the Recent Brit- ish Ostracoda. Trans. Linn. Soc, Vol. XXVI., Pt. II., p. 353. 7. 1870.—Notes on Entomostraca taken chiefly in the Northumberland and Durham District. Nat. Hist. Trans. Northumberland and Durham, Vol, III., p. 361. 8. 1885.—Notes on Entomostraca collected by Mr. A. Haly in Ceylon. Journ.Linn. Soc, Vol. XIX., p. 293. 4 Plates. 9. Brady, G. S., and Norman, A. M., 1889.—A Mono- graph of the Marine and Fresh-water Ostracoda of the N. Atlantic and of N. W. Europe. Sec. I., Po- docopa. Trans. Royal Dublin Society. 16 Plates. 10. Brady, G. S., and Robertson, D., 1869.—Notes on a Week's Dredging in the West of Ireland. Ann. and Mflg. Nat. Hist., Ser. IV.,. Vol. III., p. 353. 5 Plates. 11. 1870.—The Ostracoda and Foraminifera of Tidal Rivers. Ann. and Mag. Nat. Hist., Ser. IV., Vol. VI., p. 1. Plates. IS. 1872.—On the Distribution of British Ostrac- oda. Ann. and Mag. Nat. Hist., Ser. IV., Vol. IX., p. 48. 2 Plates. North American Fresh-water OHracoda. 473 13. 1874.—On Ostracoda taken among the Scilly Islands., and on the Anatomy of Darwinella steven- sonii. Ann. and Mag. Nat. Hist., Ser. IV., Vol. XIII., p. 114. 2 Plates. 14. Brady, G. S., Crosskfa', W. H., and Kobertson, D., 1874.—Monograph of the Post-tertiary Entomos- traca of Scotland and parts of England and Ire- land. Palseontographical Society. 16 Plates. 15. Chambers, V. T., 1877.—New Entomostraca from Colorado. Bull U. S. Geol. and Geogr. Surv., Vol. III., p. 151. Figures. 16 Chyzek, C, 1858.—Uber die Crustaceen-Fauna Un- garns. Verhandl. der k.-k. zool.-bot. Gesellschaft in Wieu., Bd. VIII., p. 505. 17. Claus, C, 1868.—Beitrage zur Kenntniss der Ostrac- oden. I. Entwicklungsgeschichte von Cypris. Pub- lished separately in 1 868, and in Schrift. der Gesellsch . zu Beford. d. gesammt. Naturwiss. zu Marburg, Bd. IX., 1872, p. 151. 2 Taf. 18. 1892.—Beitrage zur Kenntniss der Siisswas- ser-Ostraeoden. Arbeiten aus dem zoolog. Institut zu Wien, Tome X., Heft 2. 12 Taf. 19. Daday, E. v., 1893.—Uber die Ostracoden der ITm- gebung von Budapest. Termeszetrajzi Fiizetek, Vol. XV., Part 4, 1892, p. 286. 20. Dahl, F., 1888.—Die Cytheriden der westlichen Ostsee. Zool. Jahrbucher, Bd. III., Abth. f. Sys- tematik, p. 597. 4 Plates. 21. De Kay, J.E., 1844.—Zoology of New York. Part VI., Crustacea. 13 Plates. 22. Fischer, S., 1847.—Uber die in der Umgebung von St. Petersburg vorkommenden Crustaceen aus der Ordnung der Branchioyjoden und Entomostraceen. Mem. des Sav. Etrangers, T. VI, Figure. 23. 1851.—Abhandlung iiber das Genus C^'pris und dessen bei Petersbui-g und Reval vorkommende Arten. 11 Plates. 474 Illinois State Lahoratory of Nataval History. 24. 1855.—Beitrag zur Kenutniss der Ostracoden. Abhaiidl. d. matheuiat.-physik. Classe der konigl.- Bayeiischen Akad. der AViss., YII. Band,- III. Abth., p. 635. 2 Taf. 25. FoKBEs, S. A., 1893.—A Preliminary Report on the Aquatic Invertebrate Fauna of the Yellowstone National Park, Wyoming, and of the Flathead Region of Montana. Bull. U. S. Fish Comm., 1891, pp. 207-258. 6 Plates. 26. Fric, a., 1872.—Die Krustenthiere Bohmens. Archiv der naturw. Landesdurchforschung von Bohmen, Bd. II., Abth. IV., p. 206. 27. Fric, A., and Nekut, F., 1868.—Korysi zeme Ceske. Prag. Zeits. Ziva, v. J., 1867. 28. GuERNE, J. DE, 1887.—Note sur la faune des Agores. 7 pp. Naturaliste, Paris. 29. 1893.— Un Ostracode nouveau pour la faune frangaise. Revue Biol. Nord France, 4 Annee, pp. 518-519. 30. Haldeman, C, 1843.—[Descriptions of hew Cyprids.] Proceedings Phil. Acad. Sciences, 1841-43, pp. 53, 166, 184. 31. Heller, C, 1871.—Untersuchungen iiber die Crusta- ceen Tirols. Berichten des medizinisch.-naturwiss. Vereines in Innsbruck. 2 Taf. 32. Herrick, C. L., 1879.—Microscopic Entomostraca. Seventh Ann. Rep. Geol. and Nat. Hist. Surv. Minn., 1878, pp. 81-123. 21 Plates. 34. 1887.—Contribution to the Fauna of the Gulf of Mexico and the South. Memoirs of Denison Scientific Ass'n, Vol. I., No. I. 8 Plates. 35. Herrkk, C. L., and Turner, C. H., 1895.—Synopsis of the Entomostraca of Minnesota: Copepoda, Cladocera, and Ostracoda. Second Report of the State Zoologist of Minnesota. 36. Jurine, L., 1820.—Histoire des Monocles, qui se trou- vent aux environs de Geneve. 22 Plates. North American Fresh-water Ostracoda. 475 37. Kaufmann, a., 1892.—Ueber die Gattung- Acantbo- pus Yernet und eine neue Siisswassercytheride. Zool. Anz., 1892, p. 393. 38. Koch, C. L., 1837-41.—Deutclilands Crustaceen, My- riapodeu und Arachiiiden. Heft 10, 11, 12, 1837; ' Heft 21, 1838; Heft 36, 1841. 39. LiLLJEBORG, W., 1853.—De Crustaceis ex ordinibus tribus: Cladocera, Ostracoda et Copepoda in Sca- nia occurrentibus. 27 Plates. 40. 1862.—Beskrifuing ofver tvc\ arter Crusta- ceer af orduingarna Ostracoda och Copepoda. Ofvers. af k. Vet.-Akad. Forhand., XIX., p. 391. 41. 1883.—Collections of chiefly Fresh-water Crustacea from Sweden. Special Catalogue Inter- national Fisheries Exhibition, London, p. 140. 42. Meeker, J. W., 1871.—Cypris pullipes. A new species of Cypris found in New Jersey. Am, Journ. Microsc, I., pp. 68, 97. 43. MoNiEZ, R. 1887.—Liste des Copepodes, Ostracodes, Cladoceres et de quelques autres Crustaces rccueil- lis a Lille en 1886. Bull, de la Soc. Zool. de France, T. 12, pp. 508-518. 44. 18:^8.—Faune des Eaux Souterraines du De- partement du Nord et en particulier de la ville de Lille. Ostracoda. Revue Biol. Nord France, 1 Annee, pp. 179-180, 241-257. 45. 1889.—Sur la faune du Hable d'Ault. Ostracoda. Revue Biol. Nord France, 1 Annee, pp. 277-280. 46. 1889.—Sur quelques Cladoceres et sur un Ostracode nouveaux du Lac Titicaca. Revue. Biol. Nord France, 1 Annee, pp. 419-429. 13 Figures. 47. 1891.—Entomostraces d'eau douce de Su- matra et de Celebes. II. Ostracodes. Zool. Ergeb. einer Reise in Niederlandisch Ost-Indien, p. 129. Plates. 476 Illinois State Laboratory of Natiiral Histm^y. 48. 1893.—Description d'une nouvelle espece de Cypris vivant daus les eaux thermales du Ham- main-Meskboutine. Bull. Soc. Zool. France, T. 18, No. 3, pp. 141,142. 7 figures. 49. MuLLER, 0. F. . 1792.—Entomostraca seu Insecta testacea, qua? iu aquis Danije et Noi-veoiae leperit, desci-ipsit et iconibns illustravit. Tab. 21. 60. NoKDQVisT, Osc, 1885.— Beiti-ag zur Kenntniss der inueren niannlichen Geschlechtsorgaue der Cypriden. 51. 1887.— Die Pehigis(;he und 'Piefsee-Fauna der oTOsseren iinni-scliPii Seen. Zool. Anz., X. Jahrg-., pp. 339-345, 358-3(32. 52. PL.vrEAU, F., 1867 —Recherches sur les Crustaces d'eau douce de Belo-ique. Mem. Cour. et des Sav. Etrangers, T. XXXIV. 1 Plate. 53. PoGGENPoi^, M. J., 1874.—List of the Copepoda, (JIadocera, and Ostracoda of the Environs of Mos- cow. 54. Ramdour, F. a., 1808.—Uber die Gattung Cypris Miill. und drei zu derselben gehorige neue Arten Mag. d. Gesellscli. naturforsch. Freunde zu Berlin, II. Jahrg., pp. 83-93. 1 Tab. 55. Robertson, D.. 1880.—Fauna of Scotland with spe- cial reference to Clydesdale and the Western Dis- tricts ; Fresh- and Brackish-Water Ostracoda. Proc. Nat. Hist. Soc. Glasgow, Vol. IV. 35 pp. 1 Plate. 66. Sars, G. 0., 1864.— Beretning om en i Somraeren 1863 foretagen zoologisk Reise i Christiania Stift. Nyt. Mag. f. Naturvid. 13 Bd., pp. 225-260. 67. 1889.—On some Fresh-water Ostracoda and Copepoda raised from Dried Australian Mud. Chris- tiania Vid. Selsk. Forh., 1889, No. 8. 79 pp. 8 Taf. 68. 1895.—On some South-African Entomos- traca raised from Dried Mud. Vid. Selsk. Skrift. I. Math.-Naturv. Klasse, 1895, No. 8. 8 Plates. North American Fresh-water Ostracoda. 477 69. ScHW.viJZ, C. G., 1888.—Ueber die sogeuauute Scliloim- driise der mannlichen Cypriden. Berichten der Naturforsch. Gesellseh. Freiburg, Bd. III., p. 138. 2 Plates. 60. SosTAFiic, D., 1888.—Prilog poznavanju fanne slat- kovodnih korepiijaka hrvatske. Rad. Jugoslav, akad. XCII., IX., 103-214. 61. Straus, H. E., 1821.—Meinoire sur les Cypris de la classe des Crustaces. Mem. du Museum, Vol. VII., pp. 33-61. Plates. 62. Tluner, C. H., 1892.—Notes upon the Cladocera, Co- pepoda, Ostracoda, and Rotifera of Cincinnati, with Descriptions of New Species. Bull. Sci. Lab. Den- ison Univ., Vol. VI., Pt. II., pp. 57-74. 2 Plates. 63. 1893.—Additional Notes on the Cladocera and Ostracoda of Cincinnati, Ohio. Bull. Sci. Lab. Denison Univ., Vol. VIII., Pt. I., pp. 1-18. 2 Plates. 64. 1894.—Notes on American Ostracoda, with Descriptions of New Species. Bull. Sci. Lab. Denison Univ., Vol. VIIL, Pt. XL, pp. 13-25. 2 Plates. 65. Turner, C. H., and Herrick, C. L., 1895. See 35. 66. Underw'ood, Lucien M., 1836 —List of the Described Species of Fresh-water Crustacea from America North of Mexico. Bull. 111. State Lab. Nat. Hist., Vol. II., Art. 5, p. 323. 67. Vavra, v., 1891.—tJber das Vorkoramen einer Sliss- wasser-Cytheride in Bohmen. Zool. Anz., XIV. Jahrg., p. 77. 68. 1891.—Monographie der Ostracoden Boh- mens. Archiv der naturw. Landesdurchforschung von Bohmen, VIIL Band., Nr. 3. Figures. 69. V.ivRA, v., and Fric, Ant., 1894.—Untersnchungen iiber die Fauna der Gewas.ser Bohmens. IV. Archiv der naturw. Landesdurchforschung von Bohmen, IX. Band., Nr. 2. Figures. 478 lUI.no Is State Laboratory of Natm^al History. 70. Vejdovsky, F., 1880.— puvodu fauny studnicne. Slavuostni prednaskave vyrocnim, sezeuikr41. ceske spol. nauk. v. Praze, dne 3 Cervna. 71. 1882.—Thierische Organismen der Brunnen- wasser von Prag. 8 Taf. 72. Vernet, H., 1878.—Acanthopus, un nouveau genre d'Ostracodes. Forel's Materiaux pour servir a I'e- tude de la Faune profonde du Lac Lernan. IV. Serie, 1878, p. 506. 73. ZvcHARiAS, O., 1888.—Die Tiervvelt der Eifel-Maare. Biol. Centr., 8 Bd., p. 574. 74. Zaddach, E.g., 1844.—SynopseosCrustaceorumPrus- sicorum Prodromus. 75. Zenker, W., 1854.—Monographie der Ostracoden. Wieg. Archiv f. JNaturg., XX, Jahrg., I. Bd., pp. 1-87. 6 Taf. 76. ZscHOKKE, F., 1894.—Die Tierwelt der Juraseen. Re- vue Suisse de Zoologie, T. II., p. 369. 1 Plate. Explanation of Plates. 479 EXPLANATION OF PLATES. Plate XXXIX. Limnicythere reticulata n. sp.: ventral view. Inside view of left valve of shell. Rudimentary caudal ramus. Second foot. First antenna. Third foot. Posterior dorsal part of carapace. Lhniiicythere ilUnoisensis n. sp.: lateral view. Markings on shell. Part of anterior surface of shell. First foot. Rudimentary caudal ramus. Ventral view. Plate XL. Fig. 1. Limnicythere ilUnoisensis n, sp.: view of side from below. Fig. 2. Male sexual clasping organs. Fig. 3. Second foot. Fig. 4. Third foot. Fig. 5. Second antenna of male. Fig. 6. First antenna of male. Plate XLI. Fig. 1. Cyclocypris forhesi n. sp.: lateral view. Fig. 2. Dorsal view. Fig. 3. Second antenna of female. Fig. 4. Palp of left second maxilla of male. Fig. 480 Illinois State Labo7'atory of Natural liiatory. Fig. 5. Palp of right second maxilla of male. Fig. 6. Second foot. Fig. 7. Caudal ramus. Plate XLTI. Fig. 1. Cyprinotus pellucida n. sp.: lateral view. Fig. 2. Dorsal view. Fig. 3. Markings on shell. Fig. 4. First foot. Fig. 5. Second foot. Fig. 6. Caudal ramus. Fig. 7. Gyprinotus hurlingtonensis Turner, caudal ramus. Plate XLIII. Fig. 1. Cyprinotus incongruens Ramd.: caudal ramus. Fig. 2. Anterior end of right valve, pittings indicated at X. Fig. 3. Cypris reticulata Zadd.: markings on shell. Fig. 4. Caudal ramus. Fig. 5. Cypris fuscata Jur.: caudal ramus. Plate XLIV. Fig. 1. Cypris tedudinaria n. sp.: caudal ramus. Fig. 2. First foot. Fig. 3. End of organ of Zenker. Fig. 4. Second antenna. Fig. 5. Candona acuminata Fisch.: first foot. Fig. 6. Second foot. Fig. 7. Caudal ramus. Plate XLV. Fig. 1. Candona fahceformis Fisch.: caudal ramus. Fig. 2. First foot. Explanation of Plates. 48] Fig Fig view. Fig Fig Fig Fig Fig Fig Fie: 3. Second foot. 4. CancUma sigmoides n. sp., d: lateral outline 5. Second antenna. 6. Caudal ramus. 7. Second foot. 8. "Sense organ" of second antenna. 9. Palp of left second maxilla. 10. Palp of right second maxilla. 11. First foot. Plate XLVI. X 1^. 1. Candona simpsoni n. sp.: second antenna of female. Fig. 2. Second foot. Fig. 3. Lateral view. Fig. 4. Ventral view. Fig. 5. First foot. Fig. 6. Caudal ramus. Fig. 7. Candona recticoAida n. sp.: second foot. Fig. 8. Second antenna of male. Fig. 9. Palp of right second maxilla of male. Fig. 10. Palp of left second maxilla of male. Fig. 11. Caudal ramus. Fig Fig Fig Fig Fig Fig valve 31 Plate XLVIF. 1. Candona reflexa n. sp.: first foot. Second foot. Caudal ramus. Cypria exsculpta Fisch.r reticulations on shell, Cypria ophthalmica Jur.: caudal ramus. Cypria dentifera n. sp.: inside view of left 2 3 4 5 6 of shell tl:82 Illinois State Laboratory of Natural History. Fig. 7. Dorsal view of shell. Fig. 8. Palp of left second maxilla of male. Fig. 9. First foot. Fig. 10. Second foot. Fig. 11. Caudal ramus. Fig Fig Fig Fig Fig Fig valve Fig Fig Fig Fig Fig Fig Plate XLVIII. 1. Cijpria olesa n. sp.: first foot. 2. Caudal ramus. 3. Second foot. 4. Palp of left second maxilla of male. • 5. Palp of right second maxilla of male. 6. Cypria pustulosa n. sp.: inside view of right of shell. 7. Lateral view of left valve of shell. 8. First foot. 9. Caudal ramus. 10. Secoud foot. 11. Cypr/'dopsis smaragdina Yavra: lateral view, 12. Rudimentary caudal ramus.