PELECYPODA—TELEODESMACEA. 



567 



anterior and one posterior lateral. Laterals often indistinct in left 

 valve. Ligament external, prominent. Pallial sinus very wide and 

 deep, differing slightly in the opposite valves. Jurassic-Recent. 



572. T. equilateralis Meek and Hayden. Cretacic. 

 Anterior and posterior sides nearly equal. Posterior end 



slightly truncated. Umbonal angle about 140 . Posterior slope 

 more convex than anterior and slightly excavated for the reception 

 of the ligament. Umbonal ridge not very distinctly marked. 

 Surface marked with small, irregular concentric wrinkles and ob- 

 scure growth lines. Length 1.7 inches; height 1 inch. 

 Montanan : Wyoming, Montana. 



573. T. virginiana Clark. (Fig. yyy, c.) Eocenic. 

 Cardinal teeth small ; laterals indistinct. Pallial sinus obscure. 



Fig. 777. Tellina declivis, left valve ; b, d, T. wi/liamsi, right valve ; 

 c, T. virginiana, left valve. ( Md. Surv. ) 



Surface covered with fine concentric growth lines. 

 Maryland, Virginia. 



574. T. williamsi Clark. (Fig. yyy t b, d.) Eocenic. 

 Posterior cardinal tooth bifid. Lateral teeth strongly developed. 



Surface covered with elevated, close-set concentric ridges or 

 lamellae. 



Aquia and Nanjemoy : Maryland, Virginia. 



575. T. declivis Conrad. (Fig. 777, #.) Miocenic-Pleistocenic. 

 Posterior end abruptly declining. Lateral teeth distinct. 

 Miocenic : New Jersey, Maryland, Virginia. Pliocenic and 



Pleistocenic : Florida. 



CLXVII. Linearia Conrad. 

 Differs from Tellina in the lengthening of the bifid cardinal 

 teeth, the rounding of the shell posteriorly and anteriorly, the sur- 

 face partially or wholly radiately ribbed ; umbonal ridge obsolete. 

 Cretacic. 



