146 NEW YORK STATE MUSEUM 



Platyceras cf. nodosum Conrad 



Plate 10, figures 10, 11 



cf. Platyceras *nodosus Conrad. An. Rep't on Palaeontology of New York. 



1841. p. 56 

 Platyceras nodosum Hall. Palaeontology of New York. 1859. 3: 473, pi. 115, 



fig. 1-6 ; pi. 116, fig. 1-4 



With this well known Oriskany species may be compared some shells 

 of smaller size in the Gaspe limestones, with nodose surface and generally 

 rounded subsymmetrical whorls. This latter feature distinguishes them 

 from the following species. 



Localities. In the shore outcrops near Grande Greve. 



Platyceras paxillifer nov. 



Plate 14, figures 13, 14 



A small shell closely coiled for 2^ volutions or throughout its length, 

 rapidly expanding and having the general aspect of a shallow Diaphoro- 

 stoma or Strophostylus ; the surface roughly corrugated concentrically, the 

 upper shoulder of the shell bearing a single row of slender spines, begin- 

 ning, in the best preserved specimens, at the end of the 2d whorl or the 

 commencement of rapid expansion, and three in number at unequal inter- 

 vals. This species represents one of the large group of spined Platycerata 

 so frequent at this period in the development of the genus, though none of 

 this type have been described from the Helderbergian fauna yet representa- 

 tives are known to occur therein, and in the Oriskany of Glenerie we have 

 the multispinous shells P. nodosum Conrad and P. subnodosum 

 Hall, which usually appear in the form of nodate casts. 



In the Onondaga limestone fauna are P. dumosum, echinatum, 

 multispinosum, fornicatum but among them all is none of the type 

 expressed in P. p a x i 1 1 i f e r. 



Locality. Upper beds about Grande Greve. 



Platyceras tortuosum Hall 



Plate 14, figures 22-25 



Platyceras tortuosum Hall. Palaeontology of New York. 1859. 3:472, 

 pi. 113, fig: 1-5 



This species, found in the form of internal and external casts in the 

 arenaceous Oriskany of New York, is apparently represented by specimens 

 which at Perce attain much greater dimensions than the New York shell. 

 The conch is a much elongated and gently twisted cone, greatly corrugated 

 longitudinally on the columellar side. The apex is exsert, the total coiling 

 not more than i ^^ volutions and the expansion rapid though regular to the 

 aperture. The stoma is considerably undulated. 



