432 Illinois State Laboratory of Natural History. 



and C. forlesi n. sp., of this paper. Of these C. Icevisy 

 C. modesta, and C. forhesi are known to occur in America. 



COMPARISON OF SPECIES. 



1 (2). Caudal ramus twice as long as its terminal claw 



(measured on front edge). C. ljevis O. F. M. 



2 (1). Caudal ramus clearly more than twice the length 

 of its terminal claw (measured on front edge). 



3 (4). Ramus nearly two and a half times the length 

 of its terminal claw; claws strong, much bent, 

 nearly smooth. C. forbesi n. sp. 



4 (3). Ramus three times the length of its terminal claw; 

 claws strong, nearly straight, weakly bent near end, 

 finely toothed ; ramus toothed on hind edge, also 

 with comb of teeth on its side. C. globosa Sars. 



Cyclocypris forbesi n. sp. (PI. XLI., Figs. 1-7.) 



A very small form, scarcely larger than Cyclocypris 

 Icevis, .55 mm. long, .39 mm. high, and .36 mm. wide. 



The shell is plump, with equal valves, translucent, of 

 a muddy sepia-brown color in alcohol, sparsely covered 

 both anteriorly and posteriorly with conspicuous hairs, 

 none evident on sides. 



Seen from the side (Fig. 1), the shape of the shell ap- 

 proaches a subelliptical form, three fourths as high as 

 long, the dorsal margin a trifle straighter than the ven- 

 tral, which is very evenly and gently convex. 



Seen from above (Fig. 2), the shape is a moderate 

 oval, thickest behind the middle, rather bluntly pointed 

 anteriorly and more so posteriorly. 



Second antennse of male, six-segment3d ; of the female, 

 5-segmented. In the female the terminal segment (Fig. 3) 

 is as long as broad, the penultimate four times as long as 

 this, while the antepenultimate is twice as long as the pe- 

 nultimate, two and a half times as long as broad, bearing 

 an unusually long sense organ near its base, reaching be- 

 yond the end of the segment. Terminal claws nearh' 

 straight, curved at tip, faintly toothed. Natatory setae 

 four times as lono- as the terminal claws. 



