96 PALEONTOLOGY OF 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 coi^parison with 

 the other forms. Mr. Conrad would appear to refer the New Jersey shells U 

 his I. capax, in the Proceedings of the Academy of Natural Sciences Philadp^ 

 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 very different shape and has a very much shorter 

 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 locality. — In the indurated green earth beneath the Middle 

 Mi^vl Be^^ at the deep cut of the Holmdel and Keyport turnpike, Mon- 

 mouth County, New Jersey. 



Idouearca antrosa. 

 Plate XIII, Fig. 6-11. 



Cucullcea antrosa, Morton. Synopsis, p. 65, PI. XIII, Fig. 6. Gabb, Synop., p. 116. 



Meek, Check-list, p. 8. 

 Idonearca antrosa (Morton). Meek, Geol. Surv. N. J., 1868, p. 725. 

 I. antrosa (Morton). Gabb. Proc. A. K Sci., Phil., 1876, p. 315. 



L neglecta Gabb. Proc. A. K Sci., Phil., 1876, p. 314, = Cucullcea neqlecta 



Gabb. Ih., 1861, p. 326. 



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

 prolonged at the postero-basal angle, very shghtly oblique with 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 beyond the 

 edge of the proportionally small ligamental area which is marked by 

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

 angulated 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; shghtly 

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



