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NEW YORK STATE MUSEUM 



the eastern Oriskany, is apparent on comparison of the faunas 

 of the several beds. While the New York Oriskany and the 

 Helderbergian faunas are intimately related, the Onondaga fauna 

 with its wealth of corals appears to be quite distinct. From 

 comparative tables published by Weller, it appears that in the 

 brachiopod element alone, the two faunas appear to be related, 

 while the most conspicuous differences are in the coral and 

 mollusk elements. These latter characteristics of the fauna led 

 Weller to say : " Both in its coral element and in its cephalopod 

 element, as well as in the remaining mollusks, there is a strong 

 suggestion in the Corniferous [Onondaga] of a recurrence, with 

 profound modifications to be sure, of the more ancient Niagaran 

 fauna, which had occupied the same province at an earlier period." 1 

 He further thinks that " it is altogether probable that the Cor- 

 niferous [Onondaga] fauna was in large part truly an evolution 

 product from the Niagaran, after that fauna had withdrawn 

 from the interior and had become isolated in some province upon 

 the border of the continent after the close of Silurian time ". 2 



The new faunal element thus introduced first makes its appear- 

 ance during late Oriskany (Decewville) time in the northwestern 

 part of the Onondaga sea. During this time, as we have seen, 

 the Esopus muds were deposited over all the eastern region, 

 representatives having been found as far north as Lake Mem- 

 phremagog. 3 Thus the Oriskany fauna became extinct in the 

 eastern portion of the interior Mediterranean sea, but continued 

 in the northwestern region where many of the old species became 

 modified. 



During this period there occurred the invasion of the new or 

 Onondaga fauna, which first became mingled with the surviving 

 Oriskanian species to constitute the Decewville fauna. Where 

 this fauna came from is an unsettled point. Weller holds that 

 its source was in the Arctic regions, but Schuchert thinks the 



1 Jour. Geol. 1902. 10:425-27. 



2 Loc. cit. p. 428. * 



3 Ami, quoted by Schuchert. Am. Geol. 1903. 32:151. 



