630 NEW YORK STATE MUSEUM 



Postscript note oy J. M. Clarke. The fauna of the beds m 

 the Naples section, lying between the horizon of last ap- 

 pearance of the Naples fauna, stated by Mr Luther to be 

 just below the base of the Grimes sandstone and the High 

 Point sandstone, can not be properly construed as a Chemung 

 fauna. The list of species cited from this thickness of 600 feet 

 contains species which in a measure occur in Chemung faunas 

 but Spirifer disjunctus is absent below the High 

 Point horizon and none of the molluscan species are foreign 

 to the higher Ithaca fauna pertaining to the Portage province 

 adjacent on the east. The frequent Dictyosponges are more of 

 Chemung habit but these bodies (Hydnoceras, etc.) got their 

 foothold in western New York directly after the disappearance 

 of the Naples fauna, and did not become freely disseminated in 

 the more eastern Chemung deposits. Thus in the correlation 

 of the faunas of the Naples section with those of the Genesee 

 river we may say with approximate accuracy that in the latter 

 the Naples or typical Portage fauna ranges through all beds 

 from the top of the Genesee shales to the top of the Wiscoy 

 shales (Cashaqua, Gardeau, Portage, Wiscoy), a thickness of 

 1211 feet. In the Naples section this fauna first appears briefly 

 in the Genesee shales, temporarily disappears, reappears with 

 the deposition of the Cashaqua shale and continues through a 

 thickness of 600 feet of sediment. It is then driven out by an 

 invasion from the east of the Ithaca fauna which held the field 

 while the sediments equivalent to the middle and later parts 

 of the Gardeau flags were deposited, and this congeries pene- 

 trated part way across the interval but did not reach the Gen- 

 esee valley. Compared with the eastern development of the 

 • fauna in its proper province, it was comparatively few both in 

 species and individuals. After holding the field during the most 

 of the stage of Gardeau deposition it was displaced by the 

 incursion of the Chemung fauna with Spirifer dis- 

 junctus, whose earliest presence was contemporaneous with 

 the desposition of the Portage sandstones. This fauna did not 

 reach the Genesee river till, as stated by Mr Luther, the horizon 



