574 GEOLOGY 



Other continents. The Devonian system has a wide distribu- 

 tion in Siberia and China, and is known at many points in southern 

 Asia. It occurs in North and South Africa, and in the Falkland 

 Islands. It has great thickness (10,000 feet) in New South Wales, 

 and has been recognized in Victoria. Rocks of this age are the 

 oldest known formations of the North Island of New Zealand. 

 The system has considerable development in South America, and 

 carries an indigenous fauna akin to the Hamilton fauna of North 

 America. So far as identified in South America, the Devonian beds 

 are referable to the upper part of the Lower Devonian, and to the 

 lower part of the Middle. 



Climatic Conditions 



Certain evidences of great diversity of climate, or of variations 

 of climate during the period, are not at hand. The Old Red Sand- 

 stone and the Catskill formation perhaps point to aridity, but this 

 can hardly be affirmed. In formations thought to be Devonian, 

 evidences of glaciation have been reported from South Africa, 1 

 but this evidence is perhaps not conclusive. 



DEVONIAN LIFE 

 I. The Marine Faunas 



When the sea partially withdrew from the North American 

 continent near the close of the Silurian period, the shallow-water 

 faunas were restricted to limited bodies of water about the conti- 

 nental border. There appears to have been a want of free com- 

 munication between these, and the life of each developed different 

 aspects according to the conditions of each embayment. When 

 the sea again advanced upon the land in the early Devonian from 

 these different embayments, the advance from each carried toward 

 the interior its own somewhat peculiar fauna. The early Devo- 

 nian life therefore consisted of the expansions of these provincial 

 faunas. They invaded the continent more or less simultaneously , 

 but they reached the interior more or less successively. The follow- 



1 Schwarz, Jour. Geol., Vol. XIV, p. 683, and David, Q. J. G. S., Vol. XLIII, 

 p. 195. 





