eo 
MIOCENE MOLLUSCA AND CRUSTACEA. 57 
of the inner margin entirely worn away. Some of them, however, show 
the surface very perfectly preserved, and the hinge and other characters 
beautifully distinct. The plications of the exterior surface are low- 
rounded, but still very distinct, and the transverse strial fine, rather even, 
and well marked, the entire characters corresponding well with those of 
shells of the species from the Yorktown, Va., and Maryland beds, except 
in the smaller size. The shells are evidently only partially grown. 
Formation and locality: All those observed are from the artesian well 
of Mr. Woolman, at Atlantic City, N. J., and are from the cabinet of the 
Academy of Natural Sciences, Philadelphia. 
Genus CARDITAMERA Conrad. 
CARDITAMERA ARATA. 
Plate rx, figs. 5 and 6. 
Carditamera arata Conrad: Foss. Shells of the Tert. Form., p. 20, PL. v, fig. 1; Foss. 
Med. Tert., p. 11, Pl. vi, fig. 2; Cat. Miocene Foss. Atlantic Slope. Proce. A. N. 
S. Phil., 1862, p. 579; Meek, Check List Miocene Foss., p. 7. 
Jompare C. aculeata Con.: Am. Jour. Conch., vol. 2, p. 73, Pl. 1v, fig. 5. 
Mr. Gonrad’s description of this species in the Fossils of the Median 
Tertiary Formations is as follows: “Shell trapezoidal, with about fifteen ribs, 
profoundly prominent, and crossed with crowded, arched, and somewhat 
squamose strize; three of the ribs on the posterior side larger than the others; 
dorsal margin slightly declining, straight; posterior margin obliquely trun- 
rated; extremity rounded; the margin dilated at the extremity of the three 
large ribs; margin within profoundly dentate posteriorly.” 
The specimen which he figures is probably from Maryland, or some 
more southern locality. There are some features of the New Jersey speci- 
mens which, although coming within the limits of his description, do not cor- 
respond to his figure, and the number of plicee do not agree with either. His 
figure gives the hinge line and base as parallel, although his description 
says the “dorsal margin slightly declining.” On the New Jersey shells the 
dorsal margin declines considerably, and the shell has eighteen to twenty 
ribs, generally twenty. The New Jersey shells, so far as I have seen them, 
are all much narrower in proportion from beak to base than his figure, and 
