333 
PALEONTOLOGY OF NEW-YORK. 
Platyceras unguiforme (n. s.). 
Plate LIX. Fig. 1, 2, 3 & 4. 
Shell oblique, arcuate, subspiral : volutions one or two, more or less 
contiguous at the apex; last volution angular, extending in a nearly 
straight or slightly curved direction towards the aperture : aperture 
oblique subovoid; peristome sinuous. 
Surface longitudinally plicate, and marked by fine crowded undulating 
lamellose striae. 
The specimens which I have referred to this species present some variety of form 
and surface marking; and it is not improbable that the examination of a larger 
number of specimens may prove that there are two distinct species, one having 
rnore numerous plications than the other. 
Fig. 1 a, 6, & 2. Views of young individuals of this species. 
Fig. 3 a. Profile view from the dorsal side, showing the spire and the broad flat plications. 
Fig. 3 b. View of the upper side of another specimen, with more numerous plications. 
Fig. 4 a , var. multicar inatum. View of the lower side of a specimen which has numerous 
narrow plications. 
Fig. 4 b, c. Views of the upper sides of similar specimens. 
Qeological position and locality. In the shaly limestone of the Lower Helderberg 
group : Albany and Schoharie counties. 
Platyceras dilatatuiii (n. s.). 
Plate LIX. Fig. 5 a - i, & 6 c. 
Shell obliquely depressed-conical, with a single minute contiguous vo¬ 
lution at the apex, below which the shell expands very rapidly, 
particularly on the lower side, while a subangular ridge may be traced 
from the apex nearly to the base : aperture subcircular or transversely 
broad-oval; peristome undulated by the more or less numerous plica¬ 
tions of the surface. 
Surface, in the young shell, marked by obscure transverse striae and more 
conspicuous longitudinal striae; while in the older shell the right side 
