GEOLOGICAL RECORD. 



69 



classes, and, in the case of Mammalia^ the past history of 

 some orders has by this means been largely unravelled. If 

 the progress of evolution has been from lowest to highest 

 this is exactly the state of affairs we should expect to find. 



We may tabulate the classes and the order of their 

 appearance in time. 



Recent 



Pleistocene ... 



Pliocene 



Miocene 



(OHgocene) 

 Eocene 



Cretaceous.... 



Jurassic 



Triassic 



Permian 



Carboniferous 



Devonian 



Silurian 



Ordovician . . . 



Cambrian 



The geological record must therefore be regarded as 

 merely a last chapter of the history of creation, a chapter 

 with enormous imperfections and numerous omissions, 

 written in a language which is capable of many delineations 



