DIASTROPHISM AND THE FORMATIVE PROCESSES 345 



consequence of it, came the extraordinary Permo-Carboniferous 

 glaciation, attended by biological changes of so pronounced a 

 nature that they have generally been regarded as the initiation of 

 the distinctive types of life of the Mesozoic era. The Permo- 

 Carboniferous events that followed the Westphalo-Carbonide 

 movement have been growing into recognition in recent years as 

 indicating a time of transition from the Paleozoic to the Mesozoic. 

 These studies give support and definiteness to that idea. 



Thus it appears that the division of Paleozoic time on the basis 

 of diastrophism, so far as present data go, does little violence to the 

 systems and time divisions already formed on stratigraphic and 

 paleontologic and other grounds, while it seems to throw distinct 

 light on the remarkable phenomena that closed the era, phenomena 

 over which not a little obscurity long has hung. 



