107 
sculptured with the concentric wrinkles; within radiated with 
strongly indented lines^ which, on the anterior margin, are 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 P. pholadiformis of Lamarck, but differs 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 strise muricated and elevated on the anterior side into 
costrn, 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- 
cuiwed, spoon-shaped, emarginate on the posterior side, and irregu- 
larly truncated at tip. 
Greatest 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 
