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 shell ; while in 

 the description he states that the posterior side is "subcuneiform." In M. 

 capax as given by his own figure the form is subcircular, 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." 



