LOWER HELDERBERG ROCKS. 
333 
Fig. 11. A fragment preserving a little more than one volution. 
Geological position and locality. In the shaly limestone of the Lower Helderberg 
group : Becraft’s mountain, Columbia county. 
Platyceras newfeeiTyi (n. s.). 
Plate LXIII. Fig. 14 a - e. 
Shell subdiscoidal, with the last volution expanded : volutions about 
three, nearly in the same plane; the first two minute and closely in- 
volved, the last one free, somewhat rapidly expanding, flattened upon 
the back and becoming ventricose towards the aperture : aperture 
rounded or broad-oval. 
Surface marked by strong transverse Or slightly oblique nodes or ridges 
upon the dorso-lateral angles of the last volution, about eleven or twelve 
on each side, which are sometimes connected by a low ridge across 
the back (the two upper volutions being rounded and free from such 
ridges). Entire surface marked by regular even threadlike longitudinal 
striae. 
This species is very remarkable in its form and surface markings; the volutions 
being more nearly in the same plane than any other form among all those before 
me, while the transverse nodes form a very striking feature. The longitudinal striae 
are very strongly developed, and the transverse striae are not visible on the upper 
part of the shell. 
In the specimen figured, the shell is preserved near the apex, while the remaining 
portion is only a cast. Another specimen, which is an older shell, is more rapidly 
expanded below, and the transverse nodes become obsolescent towards the aperture. 
Fig. 14 a. Dorsal side of the last volution. 
Fig. 14 b. View of the top of the spire. 
Fig. 14 c. The lower side of the shell. 
Fig. 14 d. Posterior view, showing, partially, the aperture. 
Fig. 14 e. Enlargement of the surface, showing the longitudinal striae. 
Geological position and locality. In the shaly limestone of the Lower Helderberg 
group : Becraft’s mountain, Columbia county. 
