96 PALEONTOLOGY OP NEW JERSEY. 



so far as those have been observed. A figure of the Alabama specimen is 

 added on the plate by the side of the New Jersey specime^^ for co>Mparison with 

 the other forms. Mr. Conrad would appear to refer the New -Terse)^ shells tt 

 his I. capax, in the Proceedings of the Academy of Natural Science i Philndp^ 

 phia, 1872, p. 54, as he figures one which he states is from New Jersey, on pi. 

 ii, fig. 2 of that volume, but on comparison with the original figure of that 

 species in the Jour. A. N. Sci., new series, vol. iii, pi. xxxv, fig. 2, one will 

 readily see that this identification must be very erroneous, as that shell, which 

 is from Mississippi, is of veiy different shape and has a very much siiorter 

 hinge-line than the New Jersey specimens, while a comparison with fig. 1 

 of the same plate will show to which the New Jersey examples belong. 



Formation and hcality. — In the indurated green earth beneath the Middlt 

 Mji'-1 Bad, at the deep cut of the Holmdel and Keyport turnpike, Mon- 

 mouth County, New Jersey. 



Idouearca antrosa. 

 Plate XIII, Kig. 6-11. 



CucuUcea antrosa, Morton. Synopsis, p. 65, PI. XIII, Fig. 6. Gabb, Syuop., p. 116. 



Meek, Checklist, p. 8. 

 Idonearca antrosa (Morton). Meek, Geol. Snrv. N. J., 1SC8, p. 725. 

 I. antrosa (Jlortou). Gabb. Proe. A. N. Sci., Phil., 1876, p. 315. 



I. neglecta Gabb. Proc. A. jST. Sci., Phil., 1876, p. 314, = Ciwiilkva rwf/lccta 



Gabb. Ih., 1861, p. 326. 



Shell subcircular in outline, or very slightly ovate from being a little 

 prolonged at the postero-basal angle, very slightly oblique witli a straight 

 hinge line, which is about half as long as the greatest length of the shell. 

 Beaks large, erect, and slightly incurved, but not projecting Ixnoud tiie 

 edo-e of the proportionally small ligamental area which is marked by 

 oblique grooves, as in all species of the group. Surface of the shell slightly 

 ano-ulated along the postero-umbonal slope and very convex; marked by 

 numerous strong concentric lines of growth at irregular distances; no radi- 

 ating strise. Hinge-plate narrow in small and medium sized specimens and 

 the teeth small, but barely bend down at their inner extremity and few in 

 number; the denticulations along the middle of the hinge vertical and 

 small. On large individuals the outer teeth are strong, from four to five 

 in number on each side, according to the size of the individual; slightly 

 declining outwardly, and the bent portion usually nearly half as long as 



