34: H. S. Williams— Devonian System of Devonshire. 



identified as in general equivalent to that of the South Devon- 

 shire limestones and thus became Middle Devonian, while the 

 Lynton fauna and the faunas of the shales of South Devon- 

 shire were assigned to the Lower Devonian because they were 

 below the Middle limestone fauna. 



There appears to be no well defined Lower Devonian fauna 

 for England nor any uniform character of deposits to represent 

 it. "What occurs below the Middle Devonian limestone is in 

 all cases fragmental ; arenaceous slates, grits, or what the Ger- 

 mans call " schists" prevail. In North Devonshire the lime- 

 stone occurs in lenticular masses in the Ilfracombe slates. In 

 South Devonshire the limestones of Plymouth, Torquay and 

 Newton are more or less massive. In Belgium and North 

 France they are represented by the Givetienne limestone. In 

 the German area it is the Eifelien Kalk and the Stringocephalus 

 limestone.- In Russia, the Urals, and in Siberia a limestone hold- 

 ing a similar fauna is seen. Below these limestones are slates, 

 conglomerates, sandstones, called by various names : Lynton, 

 Spiriferen sandstein, Gedinnien, Coblenzien, etc., in many sec- 

 tions not recognized at all ; in the more northern and western 

 districts called " lower old red." 



In North Russia, also in Wales, reaching into Somersetshire 

 (the county bordering North Devonshire on the east) are seen 

 the " old red sandstones." These are more typically represented 

 in Scotland and across the Channel in Ireland. 



During the same geological interval, while the estuary, or as 

 Professor Geikie calls them, fresh water lake deposits of the 

 Old Red Sandstone were being deposited in the north and as 

 far south as the borders of Somersetshire, sands and muds with 

 occasional layers of limestone and marine fossils were deposited 

 in North Devonshire and, still farther, in the Southern 

 Devonshire district, and in the northern parts of Europe a 

 limestone was forming continuously for all the central part of 

 the period and a rich coral and purely marine fauna occupied 

 the region. M. Charles Barrois advances the opinion that the 

 different Devonian limestones of Europe ought to be referred 

 to different Devonian stages, viz : the coral reefs of Erbray to 

 the Gedinnien, those of Brittany and Spain to the Coblenzien, 

 those of Cabrieres to the Eifelien, and those of the Ardenne to 

 the Givetienne and Frasnienne. — Fauna du Calcaire d^ Erbray, 

 p. 335, Lille, 1889. 



Much of the difficulty and confusion seen in attempts to cor- 

 relate the various sections comes, I am, convinced, from a com- 

 monly accepted assumption that formations must be correlated 

 entire, whereas, as in the above example, the lenticular lime- 

 stones of Ilfracombe undoubtedly represent the massive lime- 

 stone formation of the south, while the shales and fragmental 



