PELECYPODA—TELEODESMACEA. 



557 



Nearly circular. Concentric striae very fine. 

 Maryland, Virginia. 



538. L. smithi O. Meyer. (L. whitei Clark.) (Fig. 762, e.) 



Eocenic. 



Surface marked with strong concentric lamellae and posteriorly 

 by a shallow fold extending backward from the umbo. Margin 

 crenulated. 



Maryland-Louisiana. 



539. L. curta Conrad. (L. uhleri Clark.) (Fig. 762, a, b.) 



Eocenic and Oligocenic. 

 Similar to L. smithi in size and shape but differs in the smooth 

 margin and absence of posterior fold. 



Chickasawan-Vicksburgian : Maryland and Gulf region. 



CLV. Diplodonta Brown. 

 Thin-shelled, orbicular, convex, concentrically striate or pustu- 

 lose. Cardinal teeth two in each valve, the left anterior and the 

 right posterior bifid ; laterals obscure or absent. Adductor scars 

 continuous peripherally with the pallial line. Tertiary— Recent. 



Fig. 763. a, b, Diplodonta acc/inis, right valve ; c, d, D. hopkinsensis. ( Md. Surv. ) 



540. D. hopkinsensis Clark. (Fig. 763, c, d.) Eocenic. 



Shell globose. Umbones rather prominent. 



