﻿302 GABB'S DESCRIPTIONS OF 



Locality and -position. — White limestone, Prairie Bluff, Alabama. Collection of the 

 Academy. 



B. kecta. PI. 48, fig. 17. Shell small, subcylindrical ; spire very much de- 

 pressed ; mouth nearly straight and narrow. A cast. 



Locality and position. — Green marl, Burlington Co., N. J. Collection of the 

 Academy. 



MYSIA, Leach. 



M. gibbosa. PL 48, fig. 18. Shell subglobose ; beaks incurved ; umbones promi- 

 nent; anterior, basal and posterior edges regularly rounded; surface marked by 

 prominent, concentric ridges. 



Locality. — Delaware and Chesapeake Canal, and New Jersey. Collection of the 

 Academy. 



DIONE, Gray. 



D. Delawarensis. PI. 48, fig. 19. Shell subquadrate ; beaks small, slightly 

 incurved ; umbones small ; cardinal line gently curved. The pallial impression has 

 a deep sinus ; shell marked by concentric lines. 



Locality. — Delaware and Chesapeake Canal, and New Jersey. Collection of the 

 Academy and my collection. 



CARDIUM, Linn. 



C. abruptum. Shell long, compressed, three-fifths as long as wide ; beaks incurved 

 and slightly bent anteriorly ; umbones very prominent ; umbonal ridge parallel with, 

 and about one-third the width of the shell, from the posterior border ; it extends to 

 the base of the shell, becoming gradually rounded ; anterior side rounded iregularly ; 

 base subangular at the extremity of the umbonial ridge ; posterior side nearly straight ; 

 surface, anterior to the umbonal ridge, plain (?) ; posteriorly marked by six or more 

 radiating ridges ; hinge teeth large, anterior teeth larger than the posterior. 



Locality. — " Near Purdy," Tenn. Prof. Safford. 



This specimen, a cast sent me by Prof. Safford, although hardly perfect enough 

 to figure, is so different from anything heretofore described, that I do not hesitate 

 publishing it, since it cannot be mistaken. 



CRASSATELLA, Lam. 



C. Monmouthensis. PI. 48, fig. 20. Shell subquadrangular; beaks curved ante- 

 riorly; umbones small; umbonal ridge prominent, angular and continued to the 

 posterior basal angle ; anterior side rounded, basal gently curved, posterior angular ; 

 musculur impressions well marked. This species resembles, somewhat, C. vadosa. 



