ORISKANT SANDSTONE. 477 



Platj ceras patuluni ( 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. 



Platjceras reflexuiu ( 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 sotnewhat 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. 



ScKFACE 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. 



