622 NORTH AMERICAN INDEX FOSSILS. 



SiLURic or Ontaric. 

 Upper Siluric or 



Monroan (including Upper Cayugan) 900-1000 ft. 

 Middle Siluric or 



Salinan (lower part of Cayugan) 1000 ft. 

 Lower Siluric or 



Niagaran 1000 ft. 



The succession in western and central New York is as follows : 



SUPERFORMATION. 



Devonic — Onondaga. 



{Great hiatus and dis conformity.) 



Upper Siluric (Monroan). 



Akron dolomite (Cobleskill approximately). 

 Bertie water lime. 



{Hiatus and dis conformity.) 



Middle Siluric (Salinan). 

 Salina shales, etc. 

 Camillus shale. 

 Syracuse salt. 

 Vernon shales. 

 Pittsford shales. 



Lower Siluric (Niagaran). 



Guelph dolomite (Shelby dolomites). 

 Lockport dolomite. 

 Rochester shale. 

 Clinton group. 



Clinton limestones and shales. 



Medina sandstone. 



SUBFORMATION. 



upper Ordovicic (Queenston shales). 



In the Rochester region, the Clinton has been subdivided by 

 HartnageP^ as follows: 



"State Museum Bulletin 114, 1907. See also Chadwick, G. H., Science, N. S., 

 Vol. 28, 347. 



