LAMELLIBEAI^CHIATA OF THE LOWEE MAELS. 87 



The description thus far is taken from internal casts and their matrices, 

 and accord well with the description given by Mr. Conrad of N. cretacea. 

 But since writing the above I have obtained from the collection of the 

 Academy of Natural Sciences of Philadelphia, the type specimens of that 

 species, which preserve the shell entire. The general form and features 

 are the same, but the surface of the ribs are slightly flattened and the inter- 

 spaces deep and narrow, and tlie ribs, about thirty of w^hich may be counted 

 on the body and anterior end of the shell, are beautifully cancellated by 

 the concentric lines. The hinge area is moderately high, and is vertically 

 striated except a narrow^ border around its outer margin. The teeth are ten 

 on the posterior side, and six or seven on the anterior side of the beak. 



The casts, except for the strength of the ribs, present much the features 

 in size and proportions of Cihota miiUiradiata Gabb, but the beaks w^ere not 

 so distant, and the basal line is not emarginate at the point occupied by the 

 byssal opening of that species. These features will serve to distinguish 

 them quite readily. 



Formation and locality. — Mr. Conrad's specimen was from Haddonfield, 

 and the cast figured on the plate is from an iron-stone nodule found near 

 Keyport, New Jersey. Both are from the lower portion of the Cretaceous 

 ibrmation. 



Genus BEEYIAECA Conrad. 



(Appendix Kerr's Geol. I:^. Car., p. 3, 1872.) 



Breviarca Saffordi. 



Plate XII, Figs. 11 and 12. 



Area Saffordi Gabb. J. A. N. S., 2d ser., Vol. lY, p. 397, PL LXVIII, Fig. 37. Synop- 

 sis, p. 97. Meek, Check-list, p. 9. 



Trigonarca Saffordi (Gabb). Meek, Geol. Surv. IST. J., 1868, p. 725. 



Breviarca Saffordi (Gabb). Conrad, Proc. Acad. N. Sci. Phil., 1872, p. 55, PL 11, 

 Fig. 3. 



Shell rather small, ovately trapezoidal in outline, with strongly ventri- 

 cose valves and large, tumid, subcentral beaks, which stand prominently 

 above the hinge line, are incurved and approximate. Hinge line about two- 

 thirds as long as the entire length of the valves, with a moderately high, 

 vertically striated area, the striated portion being bounded by a plain border 



