302 C. SCHUCHERT MEDINA AXD CATARACT FORMATIONS 



The thickness here exposed is not greater than on the Genesee Eiver, nor 

 so great as on the Xiagara at Lewiston, but it exhibits all its fossil t^-pes 

 in the greatest perfection" (page 43). He then gives a generalized sec- 

 tion of the Medina, separating it into four divisions as follows : 



(1) Grey-band of Eaton. "Tlie grey or greenish grey terminal portion. . . . 



It always appears more or less as a part of the Medina sandstone, 

 possessing the same lithological features." Thickness, 2 to 10 feet. 

 = Thorold member of Grabau. 



(2) The main red sandstone mass. Red marls and sandstones "gradually 



passing into a more sandy form in the western portion of the district." 



(3) "Grey quartzose sandstone entirely distinct" from the grey-band. At 



Niagara Falls the basal sandstone, 25 feet thick, has been named the 

 Whirlpool sandstone member. These three members were later called 

 the Upper Medina and redefined as the true Medina by Grabau. 



(4) "Red marl, and marly or shaly sandstone."' Later on this member was 



called the Lower Medina and the Queenston by Grabau, who referred 

 it to the Ordovicic as the equivalent of the Richmond and Lorraine of 

 the Cincinnati series. 



C A. HarinageJ. — In 190?-*. Hartuagel gave a good account of the 

 Medina (as defined by Hall) as exposed about Eochester. Here he 

 divides it into the "Lower Medina shale" and the "Tapper Medina sand- 

 stone and shale." The former, he states, extends east to Rome, and is 

 underlain by the Oswego sandstone, wliile the latter goes 4(> miles farther 

 to Cherr}' Valley. East of Oneida County the Upper Medina is known 

 as the Oneida conglomerate and has the characteristic fossil Arthrophy- 

 cus aUeglianiense. The year before,-^ Haitnagel had clearly shown that 

 the Oneida is equivalent to the Upper Medina, as the above mentioned 

 fossil had been found near Utica, in the type section of the formation, 

 near Verona, in Oneida County, and at the falls of the Oswego. "The 

 presence of this fossil and the stratigraphic relations of the Oneida con- 

 glomerate as shown in the Mohawk Valley can leave no doubt of the 

 upper Medina age of the Oneida conglomerate." 



A. TT. Grabau. — In his well known Guide to the Geology and Paleon- 

 tology of Xiagara Falls and Vicinity, ^^ Grabau gives a good detailed de- 

 scription of the four members of the Medina and includes all in the 

 Siluric system. In 1905^^ he returns to this formation, separating the 

 lowest or fourth member from the Medina proper and placing it in the 

 Ordovicic. He states that the Oneida and Medina "were not deposited in 

 the open sea, but rather under peculiar conditions, i. e., estuarine, if not 



2s Bull. 114, N. Y. state Mus.. 1907. pp. 10-12. 

 23 Bun. 107, N. Y. State Mus.. 1906. pp. 34-35. 

 30 Bull. 45, N. Y. State Mus., 1901. pp. 87-95. 

 81 Science, vol. 22, 1905, pp. 528-529, 532-533. 



