Prosser — Hamilton and Chemung Series. 



8<) 



"Gardeau Flagstones. 

 " Ithaca Group. 



" Cashaqua Shale and Sandstone. 



" Upper Black Shale [Genesee of the later reports]. 



" Tully Limestone. 



"Moscow Shale;" 1 the upper division of the Hamilton group of the 

 later reports. 



That which especially claims our attention in the above classification is 

 the position of this group. Professor Hall clearly indicated the relative 

 position of the Ithaca group and its extension westward, stating that " in the 

 order of succession the Ithaca group follows the Cashaqua shale ; but in the 

 Genesee valley, and the counties examined this season, that group [Ithaca] 

 is entirely wanting, and will probably not be identified farther west than 

 Seneca lake." 2 In the final report the Cashaqua shales, Gardeau sandstones 

 and Portage group of this report were classed together as forming the Portage 

 group, 3 while the Ithaca group was regarded as forming the lower division of 

 the Chemung group. 4 Subsequent studies have shown the earlier to be the 

 more accurate of the two correlations. 



In the annual report of 1841, which is the last one of the series, Pro- 

 fessor Hall said that " the tabular arrangement of strata given at the conclu- 

 sion of last year's report, is fully borne out by the examinations of the past 

 season, with the exception of the Ithaca group, which cannot in most parts of 

 the district [Fourth] be identified as distinct from the Chemung." 5 



Conrad's report of 1841 contains a table of the New York formations 

 which he referred to the Silurian system, dividing the system into a lower, 

 middle and upper series, of which the following formations composed the 

 upper series : 



" 26. Oneonta Group. 



" 25. Cazenovia Group. 



" 24. Tully Limestone. 



" 23. Sherburne Group. 



" 22. Shales near Apulia. 



"21. Black Slate." 6 



Several of the formations were evidently named by Conrad, and the 

 relative succession was not correct in all cases, as for example, with the 



1 Fourth Annual Report, Fourth Geological District (Assembly Doc. No. 50, 1840), p. 453. 



2 Ibid., p. 390. 



3 Geology of New York, Part IV, 1843, p. 834. 

 * Ibid., pp. 251,259. 



5 Fifth Annual Report, Fourth Gaological District ( Assembly Doc. No. 15). 18411, p. 179. 



6 Fifth Annual Report on the Palaeontology of New York, 1841, ib'ul., p. 31. 



