*£34 
PALEONTOLOGY OF NEW-YORK. 
The three following species are straight, or slightly arcuate at the 
apex, but without volutions. 
Platyceras plicatum* 
Plate LXIY. Fig. 1-5. 
Calceola plicata : Conrad, Annual Report on the Palaeontology of New-York, 1840, p. 207. 
Shell obliquely conical, not incurved : apex acute sublateral, expanding 
and becoming ventricose below : aperture rounded, oblique ; peristome 
regularly sinuate on the right side, shorter and plain or broadly sinuate 
on the left side. 
Surface cancellated by transverse lamellose striae, and by longitudinal 
rounded or threadlike striae : one side regularly marked by broad 
rounded plications which originate at one-third or one-half the distance 
from beak to base. 
This species varies but little in its general form, being sometimes a little more 
slender. The plications are more strongly developed in some of the specimens than 
in others, and the plicated side is always more extended; the shorter side of the 
aperture sometimes showing one or two broad undulations. 
Mr. Conrad described the Calceola plicata as follows : “ Shell longitudinally 
u striated ; plicated towards the aperture, the margin of which is waved.” The 
original specimen labelled by Mr. Conrad leaves no doubt of the species to which 
this name was applied. 
Fig. 1. A young specimen in which no plications are developed. 
Fig. 2. A more slender specimen in which the plications are strongly marked. 
Fig. B & 4. A larger individual, in which the plications are but moderately developed. 
Fig. 5. A large specimen which is compressed, the view showing a width greater than the 
natural width of the shell. 
Geological position and locality. In the shaly limestone of the Lower Helderberg 
group : Albany and Schoharie counties. 
