I i 



322 MARINE SHELLS 



Cabinet of the Academy and Philadelphia Mu- 

 seum. 



A common shell. Pennant, in his observations up- 

 on P. parva says, " I have a piece (of wood) filled 

 with them, which was found near Pensacola, in 

 West Florida." May not this have been the young 

 of our truncata ; or have we in reality the parva to 

 add to our catalogue? Pennant's figure (volume iv. 

 British Zool. pi. 40, fig. 13,) of that species does 

 not represent a truncature at the posterior side of the 

 shell ; otherwise ours might be supposed to be a va- 

 riety of it, although it attains to a much larger size. 



3. P. *cuneiformis. — Shell subcuneiform ; ante- 

 rior margin nearly closed, transversely truncated 

 from the hinge; the surface transversely striated in 

 an undulated manner, with elevated, minutely cre- 

 nate lines ; the interstitial lines smooth ; these lines 

 partially interrupt a profoundly impressed longitudi- 

 nal sulcus, which passes from the beak to near the 

 middle of the base ; the inferior portion of this mar- 

 gin is destitute of striae. ; posterior margin attenuated 

 by nearly rectilinear edges, to a rounded tip ; sur- 

 face transversely wrinkled : hinge callous, composed 

 of the reflected margin, which forms a cavity before, 

 and is destitute of cells ; dentiform process incurved, 

 slender, filiform ; hinge plate ovate-triangular, with 

 a short projecting angle on the anterior middle, and 

 subacute behind ; within, disk slightly contracted by 

 an elevated line corresponding with the external 

 sulcus. 



