292 C. SCHUCHERT MEDINA AKD CATARACT FORMATIONS 



Of these 54 species, 24 also occur in the Brassfield, 7 in the Medina, 10 

 are restricted, while 30 pass upward into the Clinton or higher formations. 



Relation to the Silunc of Anticosti. — The Cataract does not readily 

 correlate with the Anticosti section^- because of the marked differences 

 and generalized character of the faunas there, and more especially be- 

 cause of the long range of most of the species. With the Becsie River, 

 the only guide fossil in common is Coelospira planocotivexa (appearing 

 about 70 feet above the base of the Becsie Eiver) ; but the Anticosti in- 

 dividuals are only half grown compared Avith those of the Cataract, a 

 condition seemingly in harmony with the conclusion that the latter are 

 of a younger time. Then the absence in the Cataract of the Becsie River 

 guide, Clorinda harrandei, also seems to indicate that the former forma- 

 tion is of younger age. At the top of the Becsie River, however, the 

 fauna is more like that of the Cataract, and this similarity continues in 

 the succeeding 300 feet of the Gun River formation. 



On the other hand, the Brassfield of Ohio correlates more readily with 

 the Anticosti section and apparently best with zone Dg of the Gun River, 

 which is from 240 to 305 feet above the Becsie River. It is here that 

 Tnpiecid insularis (compares with T. ortoni of Ohio) and Stricklandinia 

 lens (compares mth S. triplesiana of Ohio) appear for the first time. 

 That the correlation can not be made witli the next higher zone, Dg, is 

 attested by the presence here of Atrypa reticularis, Pentamerus ohlongus, 

 and Coelospira hemisph erica, species that in New York and Ontario are 

 not seen below the Clinton. For these reasons, then, it may be said that 

 the Brassfield, Cataract, and Medina seem to hold the horizon of the 

 lower part of the Gun River formation, or more exactly from Dg to Dg, a 

 thickness of 178 feet. From these statements it will be seen that this 

 correlation is different from that by Schuchert and Twenhofel in 1910, 

 where the "Ohio Clinton,^' now the Brassfield, was correlated with the 

 zones Dg and E^.g. Further, the Medina was then doubtfully placed be- 

 .neath the Brassfield and correlated with most of the Gun River, whereas 

 now, by regarding the Medina and Brassfield as equivalents of each 

 other and of the Cataract, and with a better knowledge of all three for- 

 mations, it appears better to regard them as equivalents of zones Dg to Dg 

 of the Gun River formation. 



CONTACTS BETWEEN THE MEDINA, CATARACT, AND CLINTON ' 



At Rochester, where the Clinton appears to be fully represented, there 

 seems to be no break in deposition, or at least a very slight one, between 

 the Medina sandstone and the lowest member of the Clinton — the Sodus 



Schuchert and Twenhofel : Bull. Geol. Soc. Am., vol, 21, 1910, pp. 704-710. 



