340 NEW YORK STATE MUSEUM 



sculpture casts from the shales the suture shows as a fine line over the rest 

 of the surface. Exterior marked by obscure concentric lines. A small 

 uncompressed specimen from the limestone concretions has a hight of 5 

 mm, apertural diameter of 6]/ 2 mm. 



An example from the shales which is compressed has a diameter of 23 

 mm and a hight of 10 mm. 



These shells are rare ; further knowledge of them may prove that they 

 are specifically identical with P. s t y 1 i o p h i 1 a. 



Habitat. Genesee province ; Naples subprovince. In the soft .shales 

 at Naples and the concretions at Whetstone gully, Honeoye lake. 



PTEROPODA 



protospirialis gen. nov. 

 Protospirialis minutissima Clarke 



Plate 20, fig. 15-19 



Platyostoma ? minutissima Clarke, U. S. Geol. Sur. Bui. 16. 1885. p. 55. 



This minute and tenuous shell has the aspect of a small Platyostoma 

 (Diaphorostoma). Its apex is minute, its whorls expand very rapidly and 

 are not more than three or four in number. All are convex, the spire short, 

 the body whorl very ventricose, the aperture subcircular, outer lip thin, 

 inner lip slightly reflected, scarcely covering the umbilicus. The surface is 

 smooth or with the fine concentric lines usual to Platyostoma. Almost 

 without exception the shells present the same proportions, measuring about 

 1.5 mm in hight and width, never exceeding this size and rarely falling 

 below it. 



These delicate and diminutive shells occur in immense numbers at cer- 

 tain spots in the Naples section. In the concretionary goniatite layer lying 

 near the lower part of the shales, in Parrish gully, and at its exposures in 

 the Naples valley near Branchport, Yates, co., they are accumulated in mil- 

 lions, rivaled only in number by individuals of the pteropod Styliolina 

 fissure 11 a, with which they are associated, and in places compose the 

 rock. They occur in like abundance in the separated concretions every- 

 where through the Naples subprovince. Their nature and mode of occur- 



