406 
PALAEONTOLOGY OF NEW-YORK. 
CRlNOIDEg OF THE 0 RISK ANY SANDSTONE. 
The Crinoidese of this rock are described in connection with those of the 
Lower Helderberg group in the first part of the volume ( See page 138). 
The plates (85, 86, 87 & 88) illustrating these fossils are arranged in 
their order of sequence among those of the Oriskany sandstone. 
BRACHIOPODA OF THE ORISKANY SANDSTONE. 
The generic identity of the Brachiopoda of this rock with those of the 
Lower Helderberg group has already been noticed. The most marked 
difference consists in the generally larger size of the species of the same 
genera, and in the great number of individuals of the same species; while 
the absence of Pentamerus (with the exception of an obscure specimen) 
from the strata of this age in New-York is remarkable, and the Genus Me- 
rista, so far as we at present know, is represented onlyin a single species. 
IHsriiia grandis (n. s ). 
Plate XCII. Fig. 1 a, b, c, d. 
Shell suborbicular or very broadly oval. Dorsal valve very convex, the 
convexity equalling about one-third of the width : apex subcentral. 
Ventral valve nearly flat : apex somewhat excentric, very slightly 
elevated in front of the foramen, and the space between this and the 
anterior margin slightly concave ; foramen oblong, narrow oval, the 
depression on the exterior of the shell extending from the apex to near 
the posterior edge. 
Surface marked by strong elevated concentric lamellose striae, and, on 
the interior of the shell, by radiating vascular impressions. 
