336 PALEONTOLOGY OP NEW-YORK. 



Platyceras pyraiuidatuiii ( n, s.). 



Plate LXIV. Fia. 7, 8 & 9. 



Shell pyramidal, somewhat obtusely quadrangular and ventricose below, 



prolonged above into a central slightly inclined elongato-conical apex : 



aperture subquadrangular, 

 SuEPACE 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-conical. 



The shell is mostly exfoliated from the surface in tlie specimens figured; some 

 remains of the transverse striae being visible, though the longitudinal strise 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 arcuatuiii ( n. s.). 



Plate LXV. 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 striaa, 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. Fra. 1 a, b. 

 Shell small, consisting of about two volutions, the first minute and 

 rounded ; the last one becoming free, spreading and subquadrangular 



