CHAPTER V. 



CENOZOIC ERA. AGE OF MAMMALS. 



THIS is reckoned a primary division an Era because 

 there is just here a very general break in the rock-system, 

 and a very great change in the life-system. It is also 

 called an Age, because a new and higher dominant class 

 appears here. In Europe, the unconformity is universal, 

 and, as might naturally be expected, there is an appa- 

 rently sudden change in the life-system. But in America 

 the Laramie is not only everywhere conformable with the 

 Cretaceous beneath, but in many places also with the 

 Tertiary above ; so that the record is almost continuous. 

 And yet, at the same level, viz., between the Laramie 

 and the Tertiary, we find an enormous change of life- 

 forms. It is impossible to account for this, unless we 

 admit that the steps of progress were quicker at this 

 time. 



General Characteristics. In a geological sense, 

 modern history commences here. Modern types of ani- 

 mals and plants, modern aspects of field and forest, were 

 fairly inaugurated. Now was established in broad outline 

 the present order of things the present rulers on land 

 (except man), in the seas, and in the air ; the present 

 adjustment of the orders of animals and plants. Hence 

 the name, " Cenozoic." Some of these characteristics, 

 however, especially the introduction of Dicotyls, and 

 therefore the aspect of forests, were anticipated in the 

 Cretaceous. As there is now a new and higher dominant 



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