IV. CENOZOIC TIME. 



It has been observed that, before the close of Mesozoic time, the medieval 

 features of the era were already passing away. The Cycads had mostly 

 given place to the Sassafras, Tulip tree, Willow, Maple, Oak, and Palm ; the 

 ancient type of Ganoids, to Salmon, Perch, and Herring ; and the Corals, 

 Echini, and Mollusks had close relations to those of existing seas, though of 

 extinct species. But, notwithstanding these changes, the Mesozoic aspect 

 continued to the end. Even the little Mammals, which appeared among the 

 Reptiles, bore the mark of the age, for they approximated to the oviparous 

 Reptiles and Birds, in being themselves either semioviparous or oviparous ; 

 that is, either Marsupials or Monotremes. 



But with the opening of the new era, the Mammals in their turn became 

 the dominant race. Types much like those of the age of Man were multi- 

 plied among them, in all departments of nature. As the era advanced, 

 the first of the species now living appeared, — a few among multitudes that 

 became extinct ; and afterward a larger proportion ; and, before it closed, 

 nearly all kinds of life, excepting Mammals, were identical with those of the 

 present era. As the Paleozoic or ancient life was followed by the Mesozoic 

 or Medieval, so now there was as marked a change to the Cenozoic or recent 

 life and world. 



Cenozoic time embraces two eras : — 



I. The Tertiary, or era of Mammals. 

 II. The Quaternary, or era of Man. 



These eras, like consecutive eras in preceding time, were continuous in 

 life through both the vegetable and animal kingdoms, and it is not proved 

 that Man, the most characteristic feature of the Quaternary, was not in 

 existence before the close of the Tertiary. But one of the grandest and 

 most sweeping catastrophic epochs intervened between the two, the Glacial, 

 and so separated them, although the destructive influence of this epoch did 

 not extend over tropical regions, except in the vicinity of lofty mountains. 



TERTIARY ERA. 



The Mammals of the Tertiary era are all extinct ; and the proportion of 

 living Invertebrates, the Protozoans excluded, varies from none in the 

 earlier part of the era to 95 per cent in the later part. The Early and 

 Middle Quaternary Mammals are largely extinct, but the Invertebrates 

 and Plants are existing species. The Later Quaternary or Recent animals 

 and plants are of existing species, except those that have become extinct 

 through the agency of man. 



