MIOCENE MOLLUSC A 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. X, and are from the cabinet of the 

 Academy of Natural Sciences, Philadelphia. 



Genus CAEDITAMERA Conrad. 

 Carditamera arata. 

 Plate ix, figs. 5 and 6. 



Carditamera arata Conrad: Foss. Shells of the Tert. Form., p. 20, PL v, fig. 1; Foss. 



Med. Tert., p. 11, PI. vi, fig. 2; Cat. Miocene Foss. Atlantic Slope. Proc. A. N. 



S. Phil., 1862, p. 579; Meek, Check List Miocene Foss., p. 7. 

 Compare G. aculeata Cou. : Am. Jour. Couch., vol. 2, p. 73, PI. iv, fig. 5. 



Mr. Conrad'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 striae ; three of the ribs on the posterior side larger than the others; 

 dorsal margin slightly declining, straight; posterior margin obliquely trun- 

 cated; 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 plicae 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 



