148 NEW YORK STATE MUSEUM 



This Species is of the simply conical type expressed by P. p 1 i c a t u m, 

 P. elongatum and P. p y r a m i d a t u m Hall of the New Scotland 

 fauna' and by P. conicum Hall of the Onondaga and Hamilton faunas'; 

 of all these it approaches most nearly P. p y r a m i d a t u m. 



Locality. Grande Greve. 



Platyceras sp. 



Plate 14, figures 5-7, 16 



Other distinct forms of this genus are indicated but material is insuf- 

 ficient for conclusive determination. Of these all are of medium size and 

 (i) one is subsymmetrical with spiral of nearly 2 volutions in apposition, 

 the body whorl expanding gradually and remaining long and slender. It 

 was thus a suberect and narrow shell. Its surface is crossed by the usual 

 coarsely concentric lines and along the periphery of the spiral are a few 

 scattered spine bases, there being none further down the whorl ; (2) a some- 

 what similar form with larger spiral, narrow, nearly symmetrical body, sub- 

 carinate periphery with a broad and low revolving furrow on each side ; also 

 a suberect shell without spines or nodes. Both of these forms are from 

 Grande Greve. (3) A more erect smooth shell, with minute and slightly 

 coiled or twisted apex, very rapidly expanding and bell shaped body, some- 

 what flattened above and expanded below ; stoma undulated, cross section 

 subcircular but not symmetrical ; surface apparently smooth. This is from 

 Perce Rock. 



Holopea cf. antiqua Vanuxem 



Plate 15, figures 12-14 



xS"^.? H o 1 o p e a antiqua (Vanuxem) Hall. Palaeontology of New York. 1859. 

 3: 294, pi. 54, fig. 2, 3 



These are obconical, rather rapidly expanding shells with moderately 

 elevated spire and evenly rounded whorls which have the proportions and 

 size of the species cited, and though we do not know the character of the 

 exterior it is evident from internal casts that it was essentially smooth or 

 with only fine concentric lines. Our specimens have a hight, in an average 

 example, of 22 mm and an apertural width of 20 mm. 



The New York specimens of H. antiqua were described from the 

 Tentaculite or Manlius limestone lying at the base of the Helderbergian 

 series. 



Locality. Grande Greve. 



' See Palaeontology of New York. 1859. 3: 334-36, pi. 64. 

 ''Idem. 1867. 4:3, pi. I, fig.13-23. 



