38 



ANNUAL REPORT OF 



ERAS 



SYSTEMS 



PERIODS 



LIFE 



Quaternary 



Pleistocene 



Man 



Cenozoic 



■ 

 Tertiary 



Pliocene 

 Miocene 

 Oligocene 

 Eocene 



Mammals the dominant class 



Mesozoic 



Cretaceous 



Jurassic 



Triassic 





Reptiles dominant 

 Birds appear 

 Earliest mammals 



Palceozoic 



Permian 



Carboniferous 



Devonian 



Silurian 



Ordovician 



Cambrian 



j Upper 

 \ Lower 

 ( Upper 

 •] Middle 

 ( Lower 



Amphibians the dominant 

 class 



Fishes dominant 



Invertebrates still dominant 



Fishes appear 



All classes of invertebrates 



Archczozoic 



Algonkian 

 Archaean 



Huronian 

 Laurentian 



Indistinct evidence of life 

 No evidence of life 



Introduction and Succession of the Class of Fishes. — We may 

 now proceed to take a brief survey of the introduction and prog- 

 ress of the class of fishes, as revealed to us by palseontological evi- 

 dence, after which we shall be better prepared to understand the 

 relations born by our local fossils to- the group as a whole. It 

 requires but a limited exercise of the imagination to picture to 

 ourselves a world essentially like the one we inhabit to-day, but 

 warmer, and tenanted only by lower groups of organisms; the 

 land mostly in the form of scattered islands, destitute of grasses, 

 deciduous trees and flowering plants, untrodden by any verte- 

 brate creature ; the sea without aquatic mammals, reptiles, fishes ; 



