14 NEW YORK STATE MUSEUM 



Schuchert (1910), in his monumental Paleogeography of North 

 America, refers the Utica of New York as the zone of the 

 Mastigograptus fauna to the top of his Ordovicic period. As 

 characterizing the shale facies of the Trenton in the Atlantic 

 province are cited the Climacograptus caudatus, 

 Corynoides curtus and Magog graptolite zones, while the 

 horizon of the Normanskill shale is correlated with the Black River 

 of New York and Kimmswick of Illinois and Missouri. The Frank- 

 fort is correlated with the Edenian and placed in the Cincinnatic 

 period, the Ordovicic period being considered as closed by the Utica 

 emergence. Paleogeographic maps of North America in the late 

 Trenton and Utica stages by Ulrich and Schuchert are given, to 

 which we will have occasion to refer. 



A new light has been shed on many problems, here involved, in 

 the Revision of the Paleozoic System by E. O. Ulrich (title 68), the 

 first volume of which appeared after this paper was written, but 

 as much of the information therein published was freely given 

 to the author in the joint field excursions in the Mohawk and Hud- 

 son valleys, its principles have been applied to a considerable extent 

 to the questions that arose in this investigation and the conclusive 

 answers obtained are clear evidence of the truth of some of these 

 principles. We have here especially in mind Ulrich's theories of 

 a multiplicity of shallow continental seas and of frequent and 

 periodic migrations of faunas from their permanent oceanic 

 habitats into these inland seas. 



In the investigation of the Utica and Frankfort shales in the 

 Mohawk valley, the entire mass of shales between the Trenton 

 limestone at the base and the Upper Siluric rocks on the top were 

 studied in the region from Cohoes at the mouth of the Mohawk 

 to the neighborhood of the city of Utica and of Holland Patent. 

 In the lower Mohawk region for the most part a broad plain 

 of deep drift intervenes between the Mohawk river bluffs and the 

 foot of the Helderberg escarpment ; only two sets of sections were 

 therefore accessible in greater numbers, one at the base of the shales 

 in the ravines near the mouths of the southern tributaries of the 

 Mohawk and another in the upper Frankfort beds in the ravines cut 

 into the lower slopes of the Helderberg escarpment. The Chucte- 

 nunda creek furnished here the most satisfactorily continuous sec- 

 tion, leading from the Trenton limestone to the Schenectady beds. 

 The Canaj-oharie creek and Flat creek at Sprakers afford two excel- 

 lent sections through the lower " Utica beds " (here distinguished as 



