Clarke — Oneonta,. Ithaca and Portage Groups. 



4<) 



illations given on pp. 452, 453. On the former it is placed between the 

 "Cashaqua shale" and the "Gardeau and Portage groups;" on the latter it is 

 given the same stratigraphic position, between the "Cashaqua Shale and 

 Sandstone " and the " Gardeau Flagstones." 



In Vanuxem's final report on the Third District ( 1*42), the Iiliaca group 

 is placed in the succession above the " Portage or Nunda group," (pp. 12, 13, 

 174). It is perfectly evident, however, from reading the accounts of both of 

 these groups, that Yanuxeni had no clear conception of the true relations of the 

 formations and w as accepting the last named division on the evidence derived 

 from the Fourth District. His description of the Itliaca group is quite brief 

 and, in the special discussions by counties, the Portage and Ithaca groups are 

 generally mentioned together without further attempt at distinction, the 

 former division being represented by the rocks w hich this author had origi- 

 nally termed the " Sherburne Flagstones." Then, as to-day, there w ere no 

 difficulties in apprehending the value of this "Itliaca group," eastward of the 

 Ithaca meridian. 



The final report on the Fourth District (1843) places a new construction 

 on the formation. On page 250, Professor Hall remarked : 



" Ithaca group. In the annual reports this name w as adopted for desig- 

 nating the highly fossiliferous shales and shaly sandstones, so well developed 

 at the inclined plane of the railroad and on the Cascadilla and Fall creeks 

 near Ithaca. Subsequently an examination of the highly fossiliferous strata 

 along the Chemung river, and particularly in Chemung county, resulted in the 

 adoption of that name as designating this portion of the system. 



" Succeeding examinations satisfied me of the identity of the formations 

 at Ithaca with those of Chemung, and this opinion was advanced in the 

 annual report of 1841. 



"The reasons for merging the two in one were stated to be the impossi- 

 bility of identifying them as distinct by any characteristic fossils. The same 

 opinion is still entertained after a full examination of the strata, and a com- 

 parison of the fossils collected here and elsew here in w ell authenticated 

 localities of the Chemung. There is scarcely a fossil know n at Ithaca which 

 is not found at numerous other localities; though it is true not only of Itliaca 

 but of many other places that some of the fossils are confined to a single 

 locality in which they occur." 



Largely in consequence of this opinion, the term thereafter passed into 

 desuetude. 

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