4SS PALEONTOLOGY OF NEW- YORK. 



Iteiissehi'ria »valis. 



Plate CVI. Fig. 2 a - /. 

 Mff;anterts~ov(J{t : IIali,, Regents' R<>port for 185C, p. 101; Palseozoic Fossils, 1857, p. CI. 



Shell longitudinally broad-oval, compressed ; lateral margins subtruncate 

 and abruptly inflected ; front rounded and rarely subangular. Ventral 

 valve slightly the more elevated, most prominent along the middle, 

 sloping gradually towards the sides : beak pointed, arched so as to 

 bring the apex above the hinge-line (in casts), but not touching the 

 opposite valve, angular along the lateral slopes. Dorsal valve regularly 

 depressed-convex : beak incurved. 



Surface marked by very faint simple radiating stri®, which become 

 obsolete on the upper part of the shell. Shell-structure finely punctate. 



Casts and much-worn or exfoliated specimens of this species, only, have come 

 under my observation : none of these have the apex of the beak entire, nor do they 

 show the character of the foramen. It is evidently very near the R. suessana, but 

 differs, however, in being larger, more compressed, and often proportionally broader. 

 Casts of this species also reseinble those of Terebratula archiaci of De Verneuh:, 

 ( DuNKER und VON Meyer, Palseontographica, dritter band, 4, pi. xxvii, f 2 ). 



Fig. 2 a. The ventral valve of a specimen, wljich partially preserves the shell on the upper 



part. 

 Fig, 2 !>• Another specimen from which the shell is partially removed. 



Fig. 2 c. Profile of the same, showing the inflected margins of the shell. The specimen has 

 been flattened by pressure. 



Fig. 2 d. Ventral view of a well-preserved cast of this species. 



Fig. 2 e. Dorsal view of the same, showing the muscular impression, imprints of the hinge- 

 plates, and the dental plates preserved in the cast of the rostral cavity of the 

 opposite valve. 



Fig. 2f. Profile view of the preceding specimen. 



Fig. 2 g. The upper portion of the preceding specimen enlarged. The indentations oo the 



hinge-line are due to marks sometimes shown on the valves of old specimens of 



some or all the species of this genus. 



Fig. 2 k. The cast of a smaller specimen, showing the muscular area and the marks of the 



adductor muscles. 

 Fig. 2 I, k, I. Dorsal and ventral views of imperfect casts of this species. 



Geological position and locality. In the Oriskany sandstone : Albany and Scho- 

 harie counties. 



