OBISKANT FAUNA OF BECBAFT MOUNTAIN 89 



and is represented in the Oriskany, Schoharie grit, Onondaga and 

 Hamilton faunas. 



Cyphaspis coelebs ( the only species ) is closely allied to C. 

 m i n 11 s c u 1 u s of the Oriskany and Onondaga. 



Gastropods. This group is characterized by an immense develop- 

 ment of the genus Platyceras, which has been but sparingly rep- 

 resented in the Siluric faunas, but attains its numeric climax in species 

 here and in the Onondaga and Hamilton. The prevalence of these 

 forms is one of the most striking characters of " Hercynian " faunas, 

 and Barrois has suggested that they may v?ith propriety be designated 

 by the name Capulian. The type Orth onychia attains its culmina- 

 tion in the Helderbergian and Ulsterian; the nodose species, w^hich 

 become abundant in the Oriskanj' and Onondaga, are represented; 

 while the lamellose species and the ventricose, platystomoid forms are 

 predominant. The spinose group, prevailing in the Onondaga and 

 Hamilton, has not been observed here. 



The genera Strophostylus and Platystoma have both 

 more abundant representation in earlier and later faunas, and are not 

 diagnostic. 



Lamellibranchs. The prolific development of pterinaeoids stands 

 in sharp contrast to their comparative paucity in the Niagaran, 

 while it is in harmony with their abundance in the Devonic. 

 (Avicula textilis, A. communis, A. obliquata, A. manti- 

 cula, A. securiformis, A. pauciradiata, etc.). A v i c u 1 o- 

 p e c t e n has a well developed representation (A. tenuilamellata, 

 A. spin 11 lifer a, A. schoharie, A. umbonata, A. bellula). 



Mytilarcas of large size and gibbous form, belonging to the 

 Devonic subgenus Plethomytilus, are abundant in individuals 

 (M. ovata, M. cordiformis). 



Conocardium has but a meager representation in the single, 

 rare species, C inceptum. This genus is but sparingly known in 

 Siluric faunas. 



A large species of Modiomorpha (M. o b 1 o n g a) ; undescribed 

 species of the genera Grammysia, Goniophora, Paracylas 

 are also known. 



