122 The Ottawa Naturalist. [October 



characteristic fossils obtained. The succession of strata in the 

 Pottsville Gap gave the following series of formations in descend- 

 ing order : 



Carboniferous 



Devonian 



Coal Measures. 



Pottsville. 



Maunch Chunk. 



Pocono. 



Catskill. 



Chemung. 



The above constitutes an unbroken though somewhat tilted 

 series which, if followed down, would be found to be continuous 

 with the Silurian system without any apparent unconformity or 

 break, and presenting a series of estuarine and terrigenous 

 deposits of the Carboniferous system, from the Coal Measures 

 proper down to the Pocono, (the probable equivalent of the 

 Horton formation of Nova Scotia according to Sir William 

 Dawson, Dr. White and other authorities), followed by the terri- 

 genous and estuarine Catskill series, and in close contact with, 

 but preceding in point of time the marine sediments of the 

 Chemung and earlier Devonian strata, with their brachiopod and 

 crinoidal faunas. 



The Pottsville formation underlies the productive Coal Mea- 

 sures* of Pennsylvania just as the so-called " Millstone grit" of 

 Nova Scotia underlies the productive Coal Measures of that pro- 

 vince. Workable seams of coal occur in the Pottsville (Lykens 

 series) as well, yet not so extensively, as in the Coal Measures ot 

 Pennsylvania. In Canada, the Millstone Grit (or Westville forma- 

 tion of the Pictou coal field) is held to be for the most part barren 

 of productive coal seams. A detailed study of the fossil floras 

 which accompany and characterize the productive Coal Measures 

 of both the Upper and Lower Coal Measures of Pennsylvania and 

 elsewhere, by Dr. White, has enabled him to locate definitely the 

 horizon of the various seams met with, and I have no doubt that 

 similar detailed palaeobotanical studies in Canada would also yield 

 important and definite results. 



* The term Coal Measures is not by any means a good formational name, 

 it is one conveying- economic and petrographical relations, and should not be 

 used in nomenclature. 



