70 PALEONTOLOGY OF NEW JERSEY. 
I have seen only two single valves of this species. These come to me 
from the cabinet at Philadelphia, and are accompanied by an old label 
which credits them to the Miocene of New Jersey, and one of the valves, 
the right one, is marked in pencil “N. J.” The type specimens were from 
the “Eastern shore, Md.,” according to Mr. Conrad, so these can not be the 
types. There is much discrepancy between the form of the shell as given 
in the observations following Mr. Conrad’s description and that shown by 
these specimens themselves, in the length of the shell principally. He states 
that it is “shorter” than M. capax; but also, that “the pallial sinus is deeper 
and more angular,” which could hardly follow in a shorter shéll; while in 
the description he states that the posterior side is “subcuneiform.” In M. 
capax as given by his own figure the form is subcireular, short behind. So 
I can only think that the term “shorter” as used in the observations referred 
to, was meant to apply to M. capax instead of to this shell, and that this 
species is rightly identified as M. plena. 
It would be a comparatively easy matter to select from a group of half 
grown Mercenaria mercenaria, specimens to correspond very nearly, in out- 
line and other principal features, to this shell. But the slightly greater 
ventricosity of the valves, a much greater thickness of the substance of the 
shell and a peculiar roughness of the surface, in which it differs from small 
“specimens of that species, are features which mark it as a distinct variety at 
least. The shell, as compared with that species, can not be said to differ 
materially in outline from the elongated or cuneiform variety of it in any 
particular whatever, and might readily be mistaken for a dwarfed and 
thickened individual, except for the features mentioned and the shorter and 
broader, or rounder lunule; and may with great propriety be considered 
only as a variety of that species. 
Prof. Heilprin has classed it in his lists as Venus. If Mercenaria is to 
be retained at all, there certainly is no reason for removing this species from 
where Mr. Conrad placed it, for it is as much a Mercenaria as the type of the 
genus. 
Locality: The specimen appears to have no more definite locality than 
“N. J.”; but is credited to the “Miocene.” 
