108 



beneath ; posterior margin, from a line extending from the beak to 

 the inferior angle of the truncature, destitute of the striaj and 

 mutic ; hinge callous, formed of the duplicature of the hinge mar- 

 gin, and destitute of cells, a small tooth upon the inner margin, 

 projecting backward ; dentiform process cui-ved, prominent, slender, 

 flat. 



Length three-fourths of an inch. Breadth one inch and seven- 

 tenths. Inhabits the southern coast. Cabinet of the Academy 

 and Philadelphia Museum. 



A common shell. Pennant, in his observations upon P. parva, 

 says, " I have a piece (of wood) filled with them, which was found 

 near Pensacola, in West Florida." May this not have been the 

 young of our truncafa ; or have we in reality the jmrva 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 pos- 

 terior side of the shell ; otherwise ours might be supposed to be a 

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



Pholas cuneiformis. — Shell subcuneiform ; anterior margin 

 . nearly closed, transversely truncated from the hinge ; the surface 

 transversely striated in an undulated manner, with elevated, 

 minutely crenate lines ; the interstitial lines smooth ; these lines 

 partially interrupt a profoundly impressed longitudinal sulcus, 

 which passes from the beak to near the middle of the base ; the 

 inferior portion of this margin is destitute of striae; posterior margin 

 attenuated by nearly rectilinear edges, to a rounded tip ; surface 

 transversely wrinkled ; hinge callous, composed of the reflected mar- 

 gin, which forms a cavity before, and is destitute of cells ; denti- 

 form process incurved, slender, filiform ; hinge plate ovate-trian- 

 gular, 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. 



Length nine-twentieths of an inch. Width four-fifths of an inch. 

 Inhabits the southern coast. Cabinet of the Academy and Phila- 

 delphia Museum. 



Is often cast ashore in old wood, which it penetrates. It bears 

 some resemblance in form to the shell represented in the Encyc. 

 Method., t. 170, fig. 5, &c. Its longitudinal sulcus is very similar 

 to that of P. crispata, but in many other respects it is closely al- 

 lied to P. pimllus, and like that species it is distinguished by two 



