34 PALiEONTOLOGY OF NEW JERSEY. 



much the appearance of a young and shallow individual of Exogyra cosfata 

 in its general shape, and particularly so in its plicated surface, but differs 

 materially in the form of the hinge and ligamental area. 



Formation and locality. — The specimen from New Jersey was presented 

 to Mr. Gabb by Dr. C. C. Abbot, of Trenton, N. J., as learned by Mr. Gabb's 

 statements under his original description cited above. But the particular 

 locality is not stated. It however retains a small amount of rather dark 

 green sand in the inside, which leads me to infer it was from the Lower Bed 

 at some locality not far from Trenton, New Jersey. 



Ostrea larva. 

 Plate III, Figs. 3-7. 



Osfrea larva Lamarck. Au. sans Yert., Yol. YI, p. 216. ! H. & M., Mem. A. Sci. and 

 Arts, Boston, Yol. Y, new series, p. 406, M. and H. Proc. A. N. S., Phil., 1856, 

 p. 286. Gabb, P. A. N. Sci., Phil., 1876, p. 320. 



0. fakata S. G. Morton. A. X. Sci., Phil., 1827, p. 50, PI. I, Fig. 2. Synop. Org. 

 Rem. Cret, U. S., p. 54, PI. Ill, Fig. 5. 



0. falcata var., nasuta Mort. Ibid., PI. IX, Fig. 6, p. 54. 



0. falcata var., mesenterka Mort. Ibid., PI. IX, Fig. 7, p. 54. 



Comp. 0.i)ellucida Meek & H. Proc. A. N. S., Phil., 1860, p. 249. Meek Invert. Pal. U. 

 S. Geol. Surv. Territ., p. 15, PI. XXYIII, Figs. 4 a, b. 



Comp. 0. {Gryphwostrea?) subalata Meek. Invert. Pal. U. S. Geol. Surv. Territ., p. 15, 

 PL XXYIII, Fig. 5. 



Shell small, strongly denticulate, and also strongly arcuate latei'ally, 

 being turned to the left when viewed on the upper side. Hinge straight- 

 ened, and usually slightly alated on each side, the left side the most dis- 

 tinctly, making the hinge-line often as long or even longer than the width 

 of the valve. Denticulations of the margins strong, sharp, and pointed on 

 the outside; numbering from three to ten, often as long as the width of the 

 valve; those of the inner edge small, forming minute serrations only, usu- 

 ally as many or even more numerous than those of the outer border. Under 

 valve deepest; ligamental fosset distinct; beak often long and pointed and 

 the surface of the valve convex. Upper valve flat on the surface, more 

 particularly so in the region of the beak. Muscular scar moderatel)" large, 

 oval, and distinct, situated near the inner margin and at about the posterior 

 third of the length of the shell. 



