142 



■ 



HISTORICAL GEOLOGY. 



Periods. Fig. 201. 



► » O 9, » o o °«™. J a 015 vj ° A o ^ o o o' 



Subcarboniferous, 



14a 



Epochs. 



Permian. 



Upper Coal Measured 



Lower Coal Measures. 



Millstone Grit. 

 Upper. 

 Lower. 

 Catskill. 



Chemung. 

 Portage. 



Hamilton. 

 Marcellus. 



Corniferous. 

 Schoharie. 

 Cauda- Galli. 

 Oriskauy. 



Lower Helderberg. 

 Salina. 

 Niagara. 

 Clinton. 



Medina. 



Cincinnati. 

 Utica. 



Trenton. 



Chazy. 



Quebec. 



Calciferous. 



Potsdam. 

 Acadian. 

 Archaean. 



