218 C. S. Prosser — Upper Hamilton and 



450 feet. Portions of this division contain abundant fossils 

 and the fauna is made up of an assemblage of Hamilton, Por- 

 tage of western New York and a few species which are found 

 in the Chemung, together with those that are peculiar to the 

 Ithaca zone. Following the "Ithaca group " are 600* feet of 

 shales containing only a few fossils which are mainly the same 

 as those of the Lower Portage. Professor Williams, who first 

 noticed and described this zone, called it the Upper Portage 

 and consequently assigned to the entire Portage of the Cayuga 

 lake region, a thickness of 1300 feet. Succeeding these 

 barren shales and sandstones are shales of different lithologic 

 character which contain the regular Chemung fauna as 

 known somewhat farther south in the typical locality near 

 Chemung, and possibly now with better exposures near 

 Waverly. In this section there has never been any ques- 

 tion as to the upper limit of the Hamilton, and no one has 

 proposed to call the rocks of the " Ithaca group " with a modi- 

 fied Hamilton fauna, a part of the Hamilton stage. The 

 Ithaca fauna was correlated differently by Vanuxem who 

 called it " a group between the Portage and Chemung," and by 

 Professor Hall who considers it the lower part of the Chemung 

 stage ; but both of these geologists overlooked the non-fossil- 

 iferous zone above, which was observed by Professor Williams, 

 who has classified the rocks of this section in a perfectly satis- 

 factory manner. 



Now if we consider the section of central New York along 

 the Chenango valley, we shall find a decided change in the 

 order of the stratigraphic character of the section, although 

 certain zones or stages may be and have been traced continu- 

 ously by several geologists from Cayuga lake into the Che- 

 nango valley. The Tully limestone and Genesee shale are two 

 stages which have been followed to a locality near Smyrna 

 village in the northern part of Chenango county. To be sure 

 they are much less in thickness than where exposed on Cay- 

 uga lake, still there is no question that they represent the 

 same geologic horizon, as has been attested by every ob- 

 server who has gone over this field. It was so understood by 

 Yanuxem, in 1812 ;f more definitely described by Prosser in 

 1887 ;J the Tully limestone mapped with this eastern exten- 



*For the thickness of these divisions of the Portage see Prosser in Trans. Am. 

 Inst. Min. Eng., vol xvi, p. 945 ; also for the thickness of the Upper Portage 

 see this Journal, HI, vol. xxxii, p. 198, where Professor Williams says: "The 

 fossiliferous zone at Ithaca is separated from the lowest beds containing charac- 

 teristic Chemung fossils by about 600 feet of nearly barren, flaggy and shaly 

 deposits, but with a few fossils which belong to the characteristic Portage fauna." 



f G-eol. N. Y., Pt. Ill, pp. 164, 169 and 292. 



\. Proc. Am. Assoc. -Adv. Sci., vol. xxxvi, p. 210, where the thickness of the Gene- 

 see shale is given as 20 feet, and the limestone layers and calcareous shales as 25 

 feet, near Upperville in Smyrna township. 



