NAPLES FAUNA IN WESTERN NEW YORK, PART 2 34 1 



rence, together with their association with this pelagic fauna, lead me to 

 suspect their pteropod nature, while their pelagic character is evident. The 

 spiral shells of living pteropods are believed to be all sinistrally coiled 

 (Spirialis, Valvatella, etc.), but this consideration can not be given great 

 weight in determining the point in hand. For these reasons, I have given 

 these fossils a generic term which indicates their probable affinities. 



hyolithus Eichwald. 1840 

 Hyolithus neapolis Clarke 



Plate 20, fig. 22-30 



Hyolithes neapolis Clarke, U. S. Geol. Sur. Bui. 16. 1885. p. 56, pi. 3, 

 fig- 4, 5 



This species has the elongate triangular form characterizing H. aclis 

 Hall of the Hamilton fauna, but is well distinguished from this and other 

 species of like proportions in the following particulars. The flat or ventral 

 side bears only fine sculpture lines concentric with the surface and no trace 

 of radial lines. The convex side is distinctly subdivided into three parts, 

 two flattened marginal areas each extending one fourth the diameter of the 

 shell and separated from the median area by narrow grooves. The median 

 area is convex and arched. This subdivision of the surface is however but 

 slightly apparent in uncompressed specimens. Concentric lines cross the 

 flattened areas, but on the median division these are raised into strong 

 wrinkles which corrugate the surface. There is no trace of radial lines. 



Dimensions. Average specimens attain a length of about 25 mm and 

 an apertural width of 8 mm. 



Habitat. Genesee province ; Naples subprovince. Common in the 

 shales at Naples, also in the concretions on Honeoye lake. Chautauqua 

 subprovince. A single small individual has been found in the shales at 

 Forestville. The species also occurs in the Wiscoy shales on Wiscoy 

 creek. 



