£76 MARINE SHELLS OF THE UNITED STATES. 



specimens thus mutilated, I have but two with the 

 perforation upon the right valve. It varies in being 

 destitute of the yellow colour within. It is probably 

 allied to T. punicea, but I have never found it so far 

 north as the coast of New Jersey. It is much more 

 elongated than the latter, the strise are far more 

 distinct, and it is entirely and always destitute of the 

 rose-coloured bauds, and lines, such as are repre- 

 sented in Horn's figure of that shell. It cannot be 

 the T. angulosa of Gmel., as that species is described 

 to be suborbicular, and to have the lateral teeth re- 

 mote, whereas the alternata has but one of the lateral 

 teeth remote. 



2. T. *jpolita. Shell transversely subtriangular, 

 minutely wrinkled concentrically, white, immacu- 

 late ; anterior margin rather shorter than the poste- 

 rior one, the hinge slope declining, in a very slightly 

 arquated line, to a subacute termination ; basal mar- 

 gin nearly rectilinear from behind the middle to the 

 anterior termination ; a lateral tooth behind the 

 primary teeth. 



Length two- fifths of an inch. 



Breadth thirteen-twentieths of an inch. 



Inhabits the southern coast. 



Cabinet of the Academy and Philadelphia Ma 

 scum. 



Not unfrequent on the beach of South Carolina 

 and East Florida. 



[to be continued.] 



