I 



CRUSTACEA— OSTRACODA. 365 



111. P.(?) acuminata Ulricli. (Fig. 1667, ;',;', ^.) Mississippic. 

 Very long and narrow, the posterior end strongly pointed. 

 Lower Waverly of Ohio. 



XLV. Bythocypris Brady. 



Shell smooth, reniform, ovate or elliptical ; left valve larger than 

 the right, overlapping it usually on both the dorsal and ventral 

 margins ; dorsal margin convex, the ventral edge straighter, some- 

 times slightly concave. 



This is a recent genus into which a number of Ordovicic- 

 Carbonic forms have been placed by Jones and others. Some ' 

 authorities question whether some or even all of these would not 

 be more naturally placed in the Siluric genus Cytherellina Jones 

 and Holl. 



112. B.(?) (Cytherellina?) robusta Ulrich. (Fig. 1667. /, /', m, n.) 



Ordovicic. 

 Elongate ; posterior end acutely rounded ; anterior end more 

 regularly rounded ; ventral margin nearly straight. 

 Stones River of Minnesota. 



113. B. (Cytherellina?) cylindrica Hall. (Fig. 1666, g, g'r.) 



Ordovicic. 



Like preceding, but valves more nearly equal and ends more 

 broadly rounded. 



Trenton of Minnesota; Trenton and Eden of the Cincinnati 

 region ; Utica of Canada. 



114. B. subaequata Ulrich. (Fig. 1669, a-d.) Eocenic. 

 Elongate, low; dorsum gently curved, almost parallel to ventral 



margin ; ends nearly equally rounded. 

 Aquia formation of Maryland. 



XLVL Cypridea Bosquet. 

 Like Cypris, but with a small, hook-like projection at the antero- 

 ventral angle. Jurassic-Cretacic. 



115. C. tuberculata var. wyomingensis Jones. (Fig. 1666, s, /.) 



Cretacic. 



Elongate; ventral border gently convex, dorsal gently concave, 

 with faint median depression; anterior hook short, thick, sharp; 

 surface pustulose. 



Bear River formation of Wyoming. 



