266 PAL-EONTOLOGY OF NEW-YORK. 



Gexls CYPRICARDIXM (n.g.). 



There are a few species of shells in this group of strata which have the 

 general form of Ctpricaedia; being very inequilateral, with a more or 

 less distinctly defined oblique posterior ridge, the umbones anterior oij 

 Bubanterior and little elevated. The surface is concentrically grooved, 

 or more or less distinctly marked by prominent ridges or imbricating 

 lamellae, and, on some of them, these lamellaa are radiatingly striated or 

 cancellated. A single well-preserved specimen shows no external liga- 

 mental area. In some species, the postero-cardinal margin becomes alate 

 or subalate. They bear some general resemblance to Modiolopsis ; but the 

 shell is apparently thicker, and is more strongly marked by concentric 

 striae and with a less conspicuous anterior muscular prominence, while 

 the aspect and general expression of the shells are quite distinct. 



Until something more definite is known of the hinge-structure, I propose the 

 above name as a provisional one for the convenience of designation. 



Cypricardiiiia lamellosa ( n. s.). 



Plate XLIX A. Fia. 1 a, b, c. 



Shell subovoid, gibbous : umbones slightly elevated ; anterior extremity 

 abruptly rounded and extending little beyond the beak, somewhat 

 contracted on the base anterior to the middle, with an undefined 

 depression extending thence nearly to the umbones ; posterior slope 

 prominent, with a scarcely defined ridge ; cardinal margin compressed, 

 obliquely sub truncated above and rounded towards the base. 



ScBFACE marked by strong elevated distant lamellae ; the surface of each 

 one showing, under a magnifier, distinct radiating striae, and sometimes 

 another set of striae cancellating the first. 



Fig. 1 a. A specimen, natural size. 



Fig. 1 6. The same enlarged to nearly three diameters. 



Fig. 1 c. Cardinal view of the same enlarged. Another specimen examined is about twice 

 the size of the one figured, or equal to two-thirds the size of figs. 1 b and 1 c. 



Geological position and locality. In the shaly limestone of the Lower Ilelderberg 



group, associated with Spirifer, Rhynchonella and Jltrypa : Albany county. 



