150 KANSAS UNIVERSITY SCIENCE BULLETIN. 



the shell preserved in the mold. The proportion of young 

 specimens to fully developed adults is about 80 : 1, probably 

 due to unfavorable environment. 



SOLENOMYA sp. 



Plate V, figure 4. 



The cast of a small Sohnomya of a comparatively low, long 

 form. The details of the surface ornamentation and the end 

 of the specimen are not preserved on the specimen figured. 

 What appears to be the long end of another individual has 

 the shorter end gone, so it is impossible to identify it spe- 

 cifically. However, I have seen no other species identical in 

 form with it. Greatest length, 11 mm ; height, 4 mm. 



Whitehorse spring, Oklahoma ; very rare. 



This species has much the form of S. biarmica de Vern., of 

 Great Britain, but the ridge in the shell in the umbo curves 

 more sharply to the rear (short end) as shown in our casts. 

 They show what are probably the traces of fine radiating 

 lines in the shell, though they are hardly distinct enough to 

 be reliable. 



EDMONDIA ROTUNDA, n. sp 



Plate VII, figures 3-36. 



Shell ovate, approaching semicircular outline, gibbous. 

 Beak gibbous, elevated, subcentrally located. The entire 

 shell is quite convex. Margins regularly rounded at both 

 extremities and rounding up to the nearly straight hinge. 

 Surface ribs impressed on the cast. Excavation formed by 

 the platform beneath the beaks plainly visible. Length, 6.25 

 mm. ; length of hinge, 4 mm, ; distance from beak to front, 

 2.5 mm. ; height, 4 mm. 



Whitehorse spring, Oklahoma ; rare. Dozier, Tex. ; rare. 



This species may be distinguished from E. camminHi, poste", 

 by its more rounded outline, greater convexity, and more 

 centrally located beak. This species is probably closely re- 

 lated to E. semiorbiculata Swallow, from near Council Grove, 

 Kan., but, judging from his description, is much smaller 

 and beaks are more prominent. 



