THE OSTRACODA 



807 



8 (7) Shell faintly reticulate, with one lateral furrow. Furca tapering to a 



seta like extremity (Fig. 1251 b). 



Limnicy there illinoisensis Sharpe 1897 



Length 0.88 mm., height 0.40 

 mm., and width 0.29 mm. Dark 

 grayish white. Flagellum two- 

 segmented. Furca cylindrical, 

 about seven times as long as wide 

 (Fig. 12516). Male grasping or- 

 gans unusually well developed. 

 Terminal claw of second antenna 

 of male armed with 3 or 4 strong 

 teeth at tip. Sandy bottoms, 

 Illinois River, bayous, and lake 

 shores. May. 



FIG. 1251. 



Limnicythere illinoisensis. (a) Dor- 

 sal view; (b) Furca; (c) Side view, 

 X 54; (d) Second antenna showing 

 flagellum, di; () Sexual organs of 

 male. 



9 (10) Abdomen without furca. Second legs not backwardly directed. 



Family DARWINULIDAE. 

 Darwinula stevensoni Brady and Robertson 1870. 



Length 0.70 to 0.80 mm. Right shell overlapping the 

 left. Abdomen ending in a cylindrical unpaired process 

 (Fig. 12520). Sandy or muddy bottoms. Georgia. (D. 

 improvisa Turner 1895, is a synonym.) 



FIG. 1252. 



FIG. 1252. 

 Darwinula stevensoni. (a) Tip of abdomen, X 166. 



10 (9) Abdomen with furca. Second legs backwardly bent. 



Family CYPRIDIDAE . . n 



11 (12) Furca rudimentary, with a long seta at tip (Fig. 1253) 13 



12 (n) Furca band-like, with claws and setae at tip (Fig. 12580). .. 16 



13 Natatory setae of second antennae long, reaching at least to tips 



of terminal claws. Second foot beak-shaped at tip, with a 

 terminal claw. . . . Subfamily CYPRIDOPSINAE . . 14 



14 (15) Shell broad from above, tumid. Second antenna five-segmented. 



Cypridopsis Brady 1868. 



Only one species in North America. The most common North 

 American os traced. . . CypridopsisviduaO. F. Miiller 1785. 



C Length 0.60 to 0.70 mm., plump. Marked dorsally and laterally 



with three prominent dark bands. Very common, wherever algae 

 are present. 



FIG. 1253. Cypridopsis vidua. Furca, X 180. 



