990 PALJEONTOtOGT 07 NEW-TORK. 



343. 5. ORBICULA? SUBTRUNC ATA (n.sp.) • 

 Pi> LXXIX. Figs. 7 a, b. 



Ovate-orbicular, depressed, marked by fine concentric striaB ; apex small, excentric ; the 

 broader extremity often subtruncate, having an appearance like Metoptoma. 



This species is abundant in some localities, covering large surfaces of the shaly sandstones, 

 or distributed through the mass. In the latter condition it is obscure and not readily detected. 



Fig. 7 a. A small fragment, with several individuals of this fpecies upon the surface. 

 Fig. 7 b. A single specimen, enlarged. 



Position and locality. In the central and upper part of the group, at Loraine and Turin, 

 and probably at other places. («<<»'< Collection.) 



344. 6. 0RBICULA1 CRASSA (n. */).). 



Pi.. LXXIX. Figs. 8a,b. 



Ovate-orbicular, with the apex near the narrower extremity ; apex obtuse ; surface 

 marked by strong concentric wrinkles, and fine radiating striae. 



These characters are preserved in the cast, a small portion only of the shell remaining 

 upon the specimen. 



Fig. 8 a. The specimen of the natural size. 



Fig. 8 b. A part of the surface enlarged, showing the concentric and radiating lines. 



Position and locality. This species was found in the intercalated calcareous strata, among 

 the shales of the Hudson-river group, two mjles northeast of Troy. 



345. 7. ORBICULA CiEL ATA (n.sp.). 



Pi.. LXXIX. Figg. 9 a, b, c. 



Orbicular, small ; apex excentric, depressed along the centre, and subplicated near the 

 margins ; surface marked by fine concentric lines and minute elevated points, giving it 

 the appearance of being covered by a poriferous coral. 



This species is readily distinguished by the fine papillose markings, which sometimes 

 appear as if depressed at the tip, resembling in some' degree the surface of the 0. punctata 



of MURCHISON. 



Fig. 9 a. A fragment of this species. 



Fig. 9 b. The fragment enlarged, to show the central depression and lateral plications. 

 Fig. 9 «. A portion of the surface still farther enlarged, showing the character and arrangement of the 

 papillae. 



Position and locality. The fragment figured is from the limestone intercalated with the 

 Hudson-river shales, near Troy ( from Dr. Skilton ) . I have a similar perfect specimen, 

 which occurs in the shales of the Blue limestone of Ohio, from Mr. Clarke, of Cincinnati. 



