88 PALEONTOLOGY OF NEW YORK. 



difference in the surface marking of this form and that of authentic specimens 

 of P. capillaria is the absence of the revolving stria) upon the lower side of the 

 last volution. 



A single extravagant form which apparently belongs to P. capillaria, is illus- 

 trated on plate 30, fig. 22. The specimen is distorted by pressure, but 

 otherwise presents the essential characters of that species, .as shown upon the 

 upper side ; while the lower side presents numerous strong revolving carinae 

 which are crossed by the sharp elevated transverse striae. 



Formation and locality. In the soft calcareous shales of the Hamilton group, 

 at and near York. Livingston county, N. Y. 



PLEUROTOMARIA ? APICIALIS. 



PLATE XXI, FIG. 12. 



Pleurotomaria apicialis, Hall. Illustrations of Devonian Fossils : Gasteropoda, pi. 20, f. 27. 1876. 



Shell turbinate, higher than wide ; spire erect. Volutions five or more, 

 gradually increasing in size to the last one which is extremely ventricose : 

 somewhat obliquely flattened on the upper side, and little expanded 

 laterally, giving an obtuse angularity at the upper limit of the periphery. 



Surface marked by strong rigid striae, which turn slightly backward from the 

 suture to the revolving band, which is situated at the upper margin of the 

 periphery, crossing which they continue in a more nearly vertical direc- 

 tion on the last volution. 



The characters of this species have only been obtained by gutta-percha 

 impressions, from moulds of the exterior of the shell. It differs from the 

 other species in the more erect spire and in the position of the peripheral 

 band — the characters visible in the latter scarcely corresponding with that of 

 ordinary Pleurotomariae, on which account it is placed, with some hesitation, 

 in this genus. 



Formation and locality. In the decomposing semicalcareous beds of the 

 Chemung group, at Nichols, Tioga county, N. Y. 



