458 
PALAEONTOLOGY OF NEW-YORK. 
Rensselaeria ovalis. 
Plate CVI. Fig. 2a-/. 
Megnnteris ovnlis : Hall, Regents’ Report for 185G, p.101; Palaeozoic Fossils, 1857, p. Gl. 
Shell longitudinally broad-oval, compressed 5 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 striae, 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. 
Gasts of this species also resemble those of Terebratula archiaci of De Verneuil 
( Dunker und von Meyer, Palseontographica, dritter band, 4, pi. xxvii, f. 2 ). 
Fig. 2 a. 
Fig, 2 b. 
Fig. 2 c. 
Fig. 2 d. 
Fig, 2 e. 
Fig. 2/. 
Fig. 2 g. 
Fig. 2 h. 
Fig. 2 i, 
The ventral valve of a specimen, which partially preserves the shell on the upper 
part. 
Another specimen from which the shell is partially removed. 
Profile of the same, showing the inflected margins of the shell. The specimen has 
been flattened by pressure. 
Ventral view of a well-preserved cast of this species. 
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. 
Profile view of the preceding specimen. 
The upper portion of the preceding specimen enlarged. The indentations on the 
hinge-line are due to marks sometimes shown on the valves of old specimens of 
some or all the species of this genus. 
The cast of a smaller specimen, showing the muscular area and the marks of the 
adductor muscles. 
Ic, l. Dorsal and ventral views of imperfect casts of this species. 
Geological position and locality. In the Oriskany sandstone : Albany and Scho¬ 
harie counties. 
