330 GEOL. AND NAT. HIST. SURVEY OF MINNESOTA. 



sufficiently modified to include the American forms that propagate 

 sexually. It is presumed that Professor Wenzel Vavra, who objects 

 to the genus Erpetocypris (221), will also object to this one. The species 

 of this group, however, are closely related both anatomically and 

 physiologically, and it is thought that most workers will welcome the 

 division of the old genus Gypris into the several genera here given. 



Shell rather thin, compressed, oval or sub-triangular, height ex- 

 ceeding half the length, dorsal margin strongly arched, ventral almost 

 straight. Valves usually unequal, the left valve overlapping the 

 right. The free edges of left valve smooth, cephalic and caudal 

 extremity usually bordered with a hyaline flange. The free cephalic 

 end of right valve usually armed with tuberculiform teeth. Natatory 

 setae of antenute reach beyond the tip of the terminal claw. Abdomi- 

 nal rami are slender, with smooth or very finely pectinated claws. 



Propagation is sexual. Copulative organs are small, with an outer 

 linguiform obtuse plate. The cylindrical core of Zenker's organ bears 

 numerous wreaths of spines. 



Cypriuotus lucougruens Ramdohr. 



Plate LXVIII, Figs. 9-16. 



IBOS.—Cypris incongrnens ^auiAohx (173), p. 86; Tiif. Ill, Figs. 1-12, 15, 16, 18-20. 



1820. — Monoculus conchaceus Jurine (98), p. 171; Pi. XVII, Figs. 7-8. 



1820.— " ruher Jurine (98), p. 172; PI. XVIII, Figs. 3-4. 



1820.— " aurantiacus Jurine (98), p. 173; PI. XVIII, Figs. 5-12. 



1821.— Cypr is fusca Straus (205), p. 59; Taf. I, Figs. 1-16. 



1844.— " aurantia Zaddach (234), p. 37. 



1844.—? " opthalma Koch (:02), H. 36, p. 17. 



1850.— " aurantia Baird (5), p. 159; Taf. XIX, Fig. 13. 



1853.— " incongruens LiUiehoTg (118), p. 119; Taf. IX, Figs. 6-7; Taf XI, Figs. 



1-4; Taf. XII, Fig. 6. 

 1855.— " aurantia S. Fischer (65), p. 650; PI. I, Figs. 29-31, 60, 61. 

 1868.— " incongruens Brady (18), p. 73; PI. XXIII, Figs. 16-22. 

 1868.— " fusca Fric and Nekut (70), p. 47, Fig. 28. 

 1872.— " /a.scrt Fric (69), p. 212, Fig. 26. 



1889.— " incongruens Brady and Norman (31), p. 73; PI. XII, Figs. 8-9. 

 1891.— " incongruens Wenzel Vavra (221), pp. 95-98; Figs. 32, 32^-326. 

 1893.— " incongruens C. H. Turner (213), p. 8; PI. I, Figs. 9-16; PI. II, Figs. 17-21. 



Length 1.35 mm. Height 0.75 mm. 



The shell is equivalve, one valve overlapping the other in front. 

 The shell is yellowish brown in color and is covered with scattered 

 hairs. 



Viewed from the side (Fig. 9) the shell is sub-reniform, widest near 

 the middle. Both extremities rounded and of nearly the same width; 

 the cephalic extremity may be a trifle narrower than the caudal. 

 Ventral margin nearly straight, other margins convex. 



