ORISKANY SANDSTONE. 
477 
Platyceras patulum (n. s.). 
Plate CXIX. Fig. 3. 
Shell subhemispheric. Spire forming about three volutions, which are 
usually contiguous, sometimes free, very rapidly expanding, the last 
one extremely ventricose and assuming a hemispheric form ; apex much 
below the plane of the last volution. Aperture nearly circular; peri¬ 
stome much expanded upon the side of the body volution, and thickening 
below in the form of a columellar lip. 
Surface transversely striated. 
The aperture is proportionally larger than in any other species examined; its 
height being greater than the length, which is more than two-thirds of the length 
of the entire shell. When the specimens are laid upon the table with the mouth 
downward, the height to the summit of the volution is half as great as the longest 
diameter of the aperture. 
Fig. 3. View of the aperture where the peristome is spread over the body volution, and 
thickened below. 
Geological position and locality. In the Oriskany sandstone : Cumberland, Md. 
Platyceras reflexum ( n. s.). 
Plate CXX. Fig. 1 - 7. 
Shell spiral, obliquely or arcuately subconical, spirally ascending; the 
apex consisting of one or two free, but closely approximating volutions; 
the body volution diverging, and spreading somewhat rapidly towards 
the aperture : aperture broad, the peristome often sinuous and some¬ 
times abruptly expanded : volutions round or subangular, and rarely 
distinctly angular, with the aperture subquadrate. 
Surface transversely striate; the striae sometimes bent abruptly back¬ 
wards on the surface, indicating the existence of a marginal notch at 
some period of growth. 
This species bears some resemblance to P. spirale of the Shaly limestone, but is a 
more robust shell, and has not the spiral ridges upon the surface, besides attaining 
a much larger size. 
