OF THE UNITED STATES. 227 



youug shell is generally orbicular, and gradually be- 

 comes proportionally more elongated as it increases 

 in size. I have found it on the coasts of Maryland, 

 Carolina, Georgia and East Florida, and my brother, 

 Mr. Benjamin Say, discovered it on the shores of 

 New Jersey. 



5. C. intortaP var. Shell convex, ovate, with 

 about twenty elevated, somewhat undulated, lines, 

 with alternate smaller ones ; lines somewhat confused 

 on the convex side of the shell, the larger lines with 

 a few slightly elevated, very thick fornicated tuber- 

 cles ; apex curving laterally, tip pointing upwards 

 and not elevated from the body of the shell. 



Inhabits the southern coast. 



Of this shell I found but a single specimen, which 

 is very imperfect. It seems to correspond very well 

 with the description of C intorta of the coast of 

 England, with the exception of the form of the 

 vertex, which in that species is said to turn down- 

 wards, whereas, iu our shell, it not only turns down- 

 wards, but the curve is continued until the tip points 

 upwards. 



6. G. *convexa. Shell very convex, obsoletely 

 wrinkled or glabrous, one side vertical, the other 

 oblique ; apex prominent, decurved, slightly inclin- 

 ing towards the oblique margin, tip generally free 

 and extending lower than the edge of the aperture ; 

 aperture suboval; diaphragm less than half the 

 length of the shell, edge simply arquated. 



