6 Bulletin 6 6 



Sherburne flagstone to the lower part of Hall's Ithaca group. 

 His classification of the Upper Devonian of New York was as 

 follows: — 



Tully limestone. 



Black shale. 



Sherburne flagstone. 



Ithaca group. 



Chemung group. 



Montrose sandstone or sandstone of Oneonta. 



In his Report for the 4th Distridl,* Prof. Hall states that in 

 the Genesee valley the Ithaca group and the Tully limestone 

 are wanting. He recognized there the following formations: — 



Portage group. 

 Gardeau group. 

 Cashaqua shale. 

 Encrinal limestone. 



In 1842 the geologists of the 3d and 4th Distridls had reached 

 opposite views as to the relation of the Ithaca group to the for- 

 mations above and below it. Mr. Vanuxem states f that he had 

 intended uniting the Sherburne and Ithaca groups into one, 

 while Mr. Hall wished to unite the Ithaca and Chemung. 

 Vanuxem, however, retained the original arrangement, only sub- 

 stituting the name Portage or Nunda group which Hall had 

 used in western New York for Sherburne. No distind; line^ of 

 division is indicated by Vanuxem between the Ithaca group 

 and the Portage below or the Chemung above. In the Report 

 for 1842,1 Vanuxem introduced the term "New York System" 

 to include all of the New York formations from the Potsdam 

 sandstone to the Chemung inclusive. The following is his 

 classification of the upper part of the New York System: — 



Catskill group. 



New York System. — Erie division. < 



Chemung group. 

 Ithaca group. 

 Portage group. 

 Genesee slate. 

 Tully limestone. 

 Hamilton group. 

 Marcel lus shales. 



Prof. Hall united the Ithaca group with the Chemung in the 



*4th Ann'l Rep't 4th Geol. Dist., p. 390, 1840. 

 t Final Rep't Surv. of 3d Geol. Dist., p. 171, 1842. 

 j Final Rep't Surv. of 3d Geol. Dist., p. 13, 1842. 



