132 



VKNERIDyE. 



C. convexa. 



Dione convexa, Deshayes, Er. Mas. Cat. (Biv.) 71 (185.3). — Reeve, Condi. Icon. pi. 10, 



fig. 40. 

 Cyt/ierea Sen/ana, Conrad, Sillini. Journ. xxiii. 345 (183.3). 



Shell oval, rather thin, valves very convex, color a dead-white or 

 with a rusty tinge, usually chalky ; inequipartite, heaks elevated, 



curving- forwards, in front of 

 which is a well-marked, heart- 

 shaped lunule ; anterior part 

 about half the length of the pos- 

 terior, coin])ressed and some- 

 what pointed ; regularly round- 

 ed behind and at base ; surface 

 marked with coarse lines of 

 growth, which are most regular 

 anteriorly ; ligament long, rather 

 sunken ; within milk-white, ])ol- 

 ished ; impressions superficial. 

 Length, one and three fourths 

 inches ; height, one and one half inches ; breadth, one inch nearly. 

 The animal has very long si})hons, united throughout, translucent, 

 with white blotches near the end, more opaque and brownish near 

 the shell. 



A few specimens have been found on Chelsea Beach, but it is 

 rare. It has l)een found about Rhode Island l)y Colonel Totten ; 

 and it has also been taken with the dredge 1»y Drs. Mighels and 

 Wood of Portland, in the harbor of that place. Nahaiit Beach, 

 alive, sometimes abundant; Marblehead Harbor, dredged in seven 

 fathoms (^Haskell) ; Saltle Island and Halifax, rare (Willis). 



Mr. Say knew it only as a fossil, in which state it occurs in the 

 tertiary formation of Maryland. 



This is by no means an attractive shell, its dead-white surface 

 leading one to regard it as some beach-worn s])ecimen of Cz/prina, 

 or perhaps of Venus tnercenaria. Its form, however, is proportion- 

 ally longer than the former, and somewhat longer than the latter ; 

 and it never attains to anything like the size of either of them. It 

 belongs to the genus CalUsta of Poll. 



Oeniis VERIUS, Lin. 1758. 



Shell inequilatei-nl, sulM)vate ; hinge with three diverging car- 

 dinal teeth in each valve ; pallial imjoression with a sinus. 



