33 PALKONTOUXiV OF NEW JERSEY. 



COHBITI.A IDONKA. 

 Platf XV, tlii. 20. 



Corbula idonea Ooiiiad: Am. Jour. Sci., 1st ser., vol. 23, p. .'Ul; Miocene Foss., p. 6, 

 PI. X, fig. 6; Pioc. Acad. Nat. Sci. Piiila., 1862, p. 572; Meek, Oheck List, p. 

 12; Heilprin, Proc. Acad. Nat. Sci. Pliila., 1887, p. 403. 



"Shell triangular, veiitricose, tliick, witli irreyular impressed concentric 

 lines on the inferior valve; superior valve with obsolete eoiicentric undula- 

 tions; the posterior subinMrgin terminal, rectilinear, ol)tusely earinated, and 

 marked posteriorly by a. longitudinal furrow; inferior valve with the ])oste- 

 rior extremity subrostrated, Hexuous, the submargin obtusely earinated, and 

 rough with transverse strire; tooth very thick and profoundly elevated." 

 (Conrad, Miocene Fossils, \^. G.) 



This is one of the largest of the American species of the genus, and is 

 a very heavy and much thickened shell, and one not easily mistaken. The 

 specimen recognized by Prof A. Heilprin among the l)orings of the artesian 

 well iit Atlantic City, N. J., is a fragment of the larger tliick valve and rep- 

 resents less than one-third of the .shell;* still it is sufficient to identify the 

 sp(M-ies and prove its occurrence in the Miocene within the State limits. The 

 specimen is in the cal)inet of the Academy of Natural Sciences at Phila- 

 delphia. 



CORBITLA SUBCONTBACTA, 11. Sp. 

 PI. XV, figs. 11-14. 



Shell small, the largest individual yet observed being rather less than 

 one-fourth of an inch in length and about one-sixth of an inch in height; sub- 

 ovate in outline, widest and shortest anteriorly, the beaks moderately large, 

 and the valves very ventricose; posterior end pointed, the postero-cardinal 

 slope narrow and very abrupt, and the umbonal ridge sharp. Surface of the 

 valves marked by a few strong concentric ridges, which are round and 

 abrupt, and are not continued on the postero-cardinal slope. Substance of 

 the shell proportionally thick. In the interior the muscular imprints are 

 well marked, while the cardinal tooth is only moderately developed, but has 

 a very distinct ridge extending from its base parallel to the margin of the 

 valve and a little below it, both on the anterior and posterior sides. 



