PELECYPODA—TELEODESMACEA. 



565 



566^. M. ovata var. ovata (Rogers). (Fig. 775, c.) Eocenic. 



Smaller, thinner and more elongate than M. ovata var. pyga and 

 with less rounded basal margin. 



Nanjemoy : Maryland. 



Fig. 775. a, b, Meretrix ovata var. pyga, left valve; c, M. ovata var. ovata ; d-J> 

 M. subimpressa. (Md. Surv.) 



CLXIV. Dosiniopsis Conrad. 

 Very similar to Meretrix but the pallial sinus is acutely angular 

 and ascending. Beside the anterior lateral teeth there is a single 

 distinct posterior lateral in the right valve with a corresponding 

 socket in the left. Posterior cardinal of right valve broad and 

 deeply channeled above. Shell rotund. Cretacic-Eocenic. 



567. D. deweyi Meek and Hayden. Cretacic. 

 Broadly oval, with length slightly exceeding height, rather thin- 

 shelled, moderately convex. Beaks nearly central, somewhat 

 gibbous and incurved to nearly meet each other. Surface marked 

 by fine and regular concentric lines. Diameter slightly less than 

 1 inch. Pallial sinus narrowly rounded at apex. 



Montanan : North Dakota, South Dakota, Montana, Colorado, 

 Wyoming, Assiniboia. 



568. D. owenana Meek and Hayden. Cretacic. 



