OBSERVATIONS UPON THE WAVERLY GROUP. 511 



Thus, the genus Phillipsia was evolved during the Kiuderhook from 

 Troetus and the genus Brachymetopus from Phsethonides. Turning now 

 to the lamellebranch mollusks, what is their evidence as to the age of the 

 -Cuyahoga shales? The genera Leiopteria, Lyriopecten, PalEeoneilo, 

 Pterinopecten, Streblopteria and particularly the forms representing them 

 have a decided Devonian habit. Crenipecten occurs in the middle Wa- 

 verly and Aviculopecten only near the summit of the series. The species 

 of Schizodus are mostly allied to Devonian types. Among the brachio- 

 Ipods Productus and Chonetes are Carboniferous genera, but in the Cuy- 

 ahoga they are sparingly represented and are mostly allied to recognized 

 Devonian groups. (JroSucterlEis more abundant than Ptoductusproper 

 The fossils which have been referred to carboniferous species seem in 

 •every case to have been incorrectly identified. Productus semirecticu- 

 latus does not occur within the Ohio Waverly. Without too greatly ex- 

 tending this discussion it would be useless to consider t he rem aining 

 groups, but enough has been said to show that theCC/uyahogashales?are 

 Devonian and lie above the Hamilton. That the fauna is unlike that of 

 the New York Chemung is explained by the different physical conditions 

 prevailing in the two basins. Professor J. J. Stevenson has recently 

 shown 1 



First, that the Chemung and Catskill deposits were laid down in a 

 -shallow basin subsiding most rapidly at the east and along a line rudely 

 parallel to the Blue ridge trend; 



Secondly, That the deposits would be much greater near the main- 

 land at the east than at two hundred miles away; so that six hundred feet 

 -or more of fine material would more than fairly represent the four thou- 

 sand feet of Chemung in eastern Pennsylvania; and 



Thirdly, that the water beyond the reach of the great land wash 

 held a Chemung fauna throughout the whole of the time of the Catskill 

 •deposit. He concludes that the series from the beginning of the Portage 

 to the end of the Catskill, forms but one period; that the deposits of the 

 Catskill were not made in fresh-water lakes; that the disappearance of 

 ■ animal life over so great a part of the area toward the close of the period 

 was due to the gradual extension of the conditions existing in south- 

 eastern New York as early, perhaps, as the Hamilton period, and that 

 the Chemung should be retained in the Devonian. Professor Stevenson 

 suspects that the westward prolongation of the Catskill may be found 

 interlocking with the Bedford and Cleveland shales For our own part 

 we should not be surprised to find that the Catskill included representa- 

 tives of our conglomerates I and II and that Ohio temporarily suffered 

 from influences which prevailed for a much longer period in New York. 

 This would make the Catskill the eastern equivalent of the Kinderhook 

 as nearly as such a parallel could be carried through series originating 

 under so diverse conditions. Our present contention is for the essential 

 1 Address before the Section of Geology of the American Association, Aug., 



:i89l. 



