107 



sculptured with the concentric wrinkles; within radiated with 

 strongly indented lines, which, on the anterior margin, arc obso- 

 lete; teeth two, rarely three, on each valve, one of which is bifid 

 at tip or grooved on the inner side, and the other usually not 

 prominent above the margin. 



Length three-fifths of an inch. Width one inch and seven- 

 tenths. Thickness eleven-twentieths of an inch. Inhabits the 

 coast of North America. Cabinet of the Academy and Philadel- 

 phia Museum. 



This shell, which has very much the aspect of a Pholas, is not 

 uncommon, but is more abundant on the southern coast. It ap- 

 proaches F. plioladiformis of Lamarck, but diflfers in not being 

 " subglabrous before." 



Pholas oblongata. — Shell thin, white, transversely much 

 elongated ; basal and hinge margins nearly parallel ; anterior and 

 posterior margins rounded ; valves transversely and longitudinally 

 striated, the stride muricated and elevated on the anterior side into 

 costae, which are more prominently and densely muricated ; hinge 

 callus polished, minutely striated transversely and longitudinally, 

 and with about twelve cells, anterior to which is a recurved mar- 

 gin of the shell, forming a cavity; dentiform process dilated, in- 

 curved, spoon-shaped, emarginate on the posterior side, and irregu- 

 larly truncated at tip. 



Grreatest length, one and one-fifth. Breadth, four inches and 

 two-fifths. Inhabits Georgia, Carolina, and East Florida. 



Very common on the southern coast, penetrating compact mud 

 or clay. Small clods of this clay are often rolled ashore by the 

 waves, either containing this species, or exhibiting proofs of hav- 

 ing been its habitation, by the numerous perforations with which 

 they are distinguished. In many places, where a bed of this mud 

 is barred by the refluent tide, these shells may be seen in consider- 

 able numbers, with a portion of the smaller side appearing above 

 the surface. It is proportionally broader than the shell figured by 

 Lister, plate 423, and it seems to be allied to P. campechensis. 



Pholas truncata. — Shell white, transversely oblong, sub- 

 pentangular ; anterior margin rostrated, obtusely cuneiform in the 

 middle ; posterior margin broadly truncated at tip ; valves trans- 

 versely wrinkled and longitudinally striated, muricated, particularly 

 on the anterior side, with small erect scales, which are not arched 



