Maryland Geological Survey 25 



The Devonian of Europe tlius presents two veiy distinct types of sedi- 

 mentation. Tlie norther]!, or continental type of sediment, is best ex- 

 hibited in northern England and Scotland and consists of red rocks usually 

 unfossiliferous but containing locally numerous remains of fresh or 

 brackish water fishes. The fish fauna was early made famous by the 

 studies of Hugh Miller upon the Old Eed Sandstone of Scotland. The 

 southern type consists of marine limestones, sandstones, and shales, con- 

 taining an extensive fauna. It outcrops in numerous areas between 

 Devonshire on the west and Russia on the east, extensive exposures occur- 

 ring in Belgium, the Ardennes, the Ehine Valley, the Hartz Mountains, 

 and in Bohemia. It probably extends under cover with little interruption 

 between the limits named. 



Turning to Xorth America the Devonian is found in two widely sepa- 

 rated areas, an eastern and a western. The western region, situated east 

 and west of the Eocky Mountains, contains strata which differ so greatly 

 from those of the east in the character of their contained organisms that 

 no further discussion of them is necessary in this connection. 



The Devonian of eastern America was first critically studied by James 

 Hall and his associates of the New York Geological Survey. Hall recog- 

 nized the following Devonian formations referring them to the Devonian 

 and upper part of the Silurian in his later work. 



Catskill 



Chemung 



Ithaca 



Portage 



Genesee 



Tully 



Hamilton 



Marcellus 



Upper Helderberg 



Cauda-Galli Grit 



Oriskany 



Lower Helderberg 



In his earliest work Hall placed the base of the Devonian at the base of 

 the Catskill which closely resembles the Old Eed Sandstone of England, 

 and referred the underlying marine fossiliferous strata to the Silurian 



