34 PALEONTOLOGY OF XEW JERSEY. 



mnch the appearance of a young and shallow individual of JExogyra costata 

 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. ilbbot, of Trenton, N. J., as learned by Mr. Gabb's 

 statements vinder 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. 



Ostrea larva Lamarck. An. 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. K S., Phil., 1856, 

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

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



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

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

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

 Comp. O.pellucida Meek & H. Proc. A. X. S., Phil., 1860, p. 249. Meek Invert. Pal. U. 



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

 Comp. 0. {Gryphceostreaf) snbalata Meek. Invert. Pal. (J. S. Geol. Surv. Territ., p. 15, 

 PI. XXYIII, Fig. 5. ' 



Shell small, strongly denticulate, and also strongly arcuate laterally, 

 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-hne 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 sma;ll, 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 moderately large, 

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

 third of the length of the shell. 



