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PALAEONTOLOGY OF NEW-YORK. 
Cypricardtnsa concentrica (n. s.). , 
Plate L. Fia. 2. 
Shell oval-ovate, broader behind, compressed, narrowed and regularly 
rounded at the anterior end : umbones extremely depressed; hinge¬ 
line scarcely curved ; base regularly curving; posterior extremity 
somewhat abruptly rounded : a defined oblique ridge from the beak 
backwards. 
Surface marked by strong concentric ridges, wdiich are more distinct on 
the anterior and central portions of the shell, and become obsolete 
above the oblique ridge. 
Fig. 2. The right valve of this species. The figure represents the shell as more acute an¬ 
teriorly, and more oblique on the posterior margin than it is in reality, while the 
concentric ridges are represented as bending too acutely upon the posterior ridge. 
Geological position and locality. In the compact calcareous layers of tlie central 
portions of the Lower Helderberg group : Schoharie county. 
Cypricardinia crassa (n. s.). 
Plate L. Fig. 3. 
Shell r thick, subrhomboidal : umbones depressed; anterior side short, 
rounded; posterior side much wider, somewhat obliquely truncated; 
hinge-line short, the oblique ridge extending to the postero-lateral 
margin. 
Surface marked by a few broad, distinct, thickened lamellae, and finer 
striae of growth. 
Fig. 3. The right valve, natural size. The posterior side is somewhat broken and obscure. 
Geological position and locality. In the shaly limestone of the Lower Helderberg 
group : Schoharie. 
