LOWER HELDERBERG ROCKS. 
329 
Surface marked by fine transverse strise and a few broad shallow 
wrinkles. 
This species has some resemblance to the P. ventricosum; but the apex is more 
minute, and in that shell the volutions expand regularly and rapidly, while in this 
one the expansion is more abrupt and the shell more extremely ventricose. This 
species shows some.transverse wrinkles, which are often preserved in the cast; but 
this feature has not been observed in P. ventricosum. 
Fig. 1. View of the upper side of the spire of a specimen where the apex is entire. The 
shell is nearly all exfoliated from the body of the specimen. 
Fig. 2. A similar but less symmetrical specimen, preserving little of the she]l, 
Fig. 3. Anterior view of fig. 1, 
Fig. 4. View of the upper side of the spire of a smaller specimen, in which the apex is 
broken off. 
Fig. 5. A smaller specimen of, apparently, the same species, having the apex broken ofi" and 
the shell compressed from above. 
Geological position and locality. In the upper part of the shaly limestone : Scho¬ 
harie and Albany counties; Becraft’s mountain. 
Platyceras ohesum ( n. s ). 
Plate LXII. Fig. 6 & 7. 
Shell large, elevated hemispheric : apex minute, lateral, from which 
the shell expands abruptly, becoming extremely ventricose in the 
middle and slightly contracted towards the margin, and again spreading: 
aperture campanulate ; peristome sinuate. 
Surface above marked only by fine transverse strise, and towards the 
aperture by short strong flattened plications, upon which the transverse 
strise are strongly lamellose. 
This species differs from the P. perlatum in the proportionally much gi’eater ele¬ 
vation, the lateral position of the apex of the spire, and the plicate margin of the 
aperture. 
Fig. 6. Lateral view of the specimen, from which the shell is nearly all exfoliated. 
Fig. 7. A portion of the peristome, from which the upper paid of the shell has been worn 
away, showing the plications. 
Geological position and locality. In the upper part of the shaly limestone at Be¬ 
craft’s mountain, and in the upper pentamerus limestone near Schoharie. 
[ Palaeontology III.] 42 
