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PALAEONTOLOGY OP NEW-YORK. 
Platyceras pyramidatum ( n. s.). 
Plate LXIY. Fig. 7, 8 & 9. 
Shell pyramidal, somewhat obtusely quadrangular and ventricose below, 
prolonged above into a central slightly inclined elongato-conical apex: 
aperture subquadrangular. 
Surface marked by a few strong plications near the aperture on one or 
two sides ; transversely marked by lamellose striae, and longitudinally? 
by rounded equal striae. 
This species is distinguished by its obtusely quadrangular pyramidal form below, 
while its extension above is rounded and elongato-coqical. 
The shell is mostly exfoliated from the surface in the specimens figured; some 
remains of the transverse striae being visible, though the longitudinal striae cannot 
be seen. 
Fig. 7 & 8. Two views of the same specimen. Fig. 9. View of a smaller specimen. 
Geological position and locality. In the upper part of the shaly limestone : Scho¬ 
harie county. 
Platyceras arcuatum (n. s.). 
Plate LXY. Fig. 6. 
Shell elongate arcuato-conical, making about one-third of a volution 
which is essentially in the same plane, gradually spreading below : 
aperture nearly round. 
Surface marked by fine transverse striae, which are undulated in passing 
over some undefined longitudinal elevations and depressions of the 
surface ; without distinct plications or visible longitudinal striae. 
Geological position and locality. In the upper part of the shaly limestone : Scho¬ 
harie county. 
Platyceras undulostriatum (n.s.). 
Plate LXV. Fig. 1 a, b. 
Shell small, consisting of about two volutions, the first minute and 
rounded; the last one becoming free, spreading and subquadrangular 
