134 KANSAS UNIVERSITY QUARTERLY. 



broadly convex anteriorly. Surface marked by moderately distinct 

 lines of growth. 



Measurements: Length, i6mm.; height, 14 mm.; convexity of 

 single valve, 4 mm. 



.Lawrence oolite, Lawrence, and also from the horizon of the 

 Osage Coal at Topeka, Kansas. 



The generic position of this shell is uncertain. It is very similar 

 to White's Af////rac-<)/'/er/s />(>/i/a, but seems specifically distinct from 

 it. The only difference between our shell and the true Mo?ioptcria 

 is that tlie posterior ear is less developed than in that genus. The 

 beak, and especially the lunule, are precisely as in Monopteria, as 

 well as the general expression of the shell. The internal charac- 

 ters are not known. It is closely allied to Monopteria sp. Keyes, 

 but its posterior ear is less developed and the umbonal ridge much 

 more curved, and the whole shell more slender than is represented 

 in his figure. Until the internal characters can be found out we 

 place it in the genus Monopteria provisionally. 



