Peossee — Hamilton and Chemung Seeies. 



165 



It will be noticed that in the above fauna Spirifer disjunct us, Sow., is 

 not reported ; but above the fauna just cited occur shales that contain a fauna 

 " very similar to that in the dark shale at the base of the Ithaca group, but 

 mingled with other species. * * * The most northern exposure, at which 

 the typical Chemung fauna was found in abundance, was high up in the hills 

 in the northeastern part of Chemung county, near Park station," 1 and at this 

 place tip infer disjunetus, Sow., and Orthis Tioga, Hall, were found, some 

 300 or 400 feet stratigraphically above the lowest fauna in Danby. 



On comparing the list of fossils reported by Professor Williams from the 

 lowest Chemung in Danby 2 with the list given by Professor Clarke for 

 Greene, 8 or the fauna reported in this paper from Chenango Forks, it will be 

 seen that all the species listed by Professor Williams from Danby, except 

 Amboccelia umbonata var. gregaria, occur in these localities in Chenango 

 county. Again it will be found that the thickness of the formations from the 

 top of the Genesee slates to the base of the fauna overlying the Oneonta of 

 the Chenango valley, and the similar fauna above the Upper Portage of the 

 Cayuga lake region is about the same. Professor Williams reports it as 

 "1,300 feet or more" 4 for Tompkins county, and in the Chenango valley it is 

 fully 1,300 feet from the top of the Hamilton to the base of the fauna imme- 

 diately above the Oneonta formation. Finally Professor Williams described 

 a fauna containing Tropidoleptus carinatus x near Owego 5 at about the same 

 altitude as the Tropidoleptus carinatus zone near Port Crane, which is in the 

 midst of a typical Chemung fauna, at least 200 feet above the first occurrence 

 of Spirifer disjunetus, Sow. It is thought that possibly the Owego zone of 

 Tropidoleptus represents the same general part of the section as that at Port 

 Crane, except that the Tropidoleptus fauna is being replaced by the regular 

 Chemung fauna near Owego, consequently it is not so conspicuous as in the 

 sections farther east. 



After reviewing the results obtained by different investigators of this 

 problem of the separation of the Chemung and Portage and the Chemung 

 and Oneonta formations in the central part of southern New York, the facts 

 seem to justify the conclusion that the Chemung begins with the Orthis 

 impressa fauna overlying the Oneonta formation. 



The thickness of the formations composing the Chenango valley section, 

 ranging from the base of the Marcellus shale in Sangerheld township, Oneida 



1 Bulletin United States Geological Survey, No. 3, 1884, p. 22. 

 3 Ibid., p. 21. 



3 Thirteenth Annual Report State Geologist [New York], p. 543. 



4 Bulletin United States Geological Survey, No. 3, |>. 21. 



5 Ibid., p. 24. 



