PALEOZOIC ROCKS AND ERA, 323 



by this revolution was sweeping. When quiet and pros- 

 perous times again commenced, in the Mesozoic, we find 

 an entirely different condition of things. It is almost 

 like a new world. We must not imagine, however, that 

 the change was absolutely sudden. The steps of change 

 here were only more rapid, and the general unconformity 

 and loss of record which occur here make it seem sudden. 



Transition to the Mesozoic Era. Permian Period. 



We have seen (page 267) that the Paleozoic commenced 

 after a great revolution. Now, the Paleozoic was closed 

 also by a similar revolution. We have called this latter 

 the Appalachian Revolution, because this range was 

 made at that time ; but it was a time of widespread 

 oscillations, and, therefore, of great changes in physical 

 geography and climate, marked by universal unconformity 

 and by sweeping changes in life-forms. Now, as already 

 seen on page 193, unconformity always means lost record 

 at that place. Of the lost record between the Archaean 

 and Paleozoic nothing has been certainly found, but of 

 that between the Paleozoic and Mesozoic, certain leaves 

 have been recovered. These are brought together and 

 called the Permian. Some have allied the Permian with 

 the Mesozoic under the name of Dyas. Others have 

 allied it with the Paleozoic. The truth is, it ought to 

 be regarded as a period of transition or of revolution 

 between the two. 



Life System. As might be expected the organisms 

 of the Permian are mainly transitional. Paleozoic forms 

 are passing away and Mesozoic forms are coming in. The 

 very first reptiles are introduced here, but they had not 

 yet attained supremacy. 



