1 6 THE HISTORY OF CREATION". 



earth, the tertiary epoch, or era of Leafed Forests, is much 

 shorter and less peculiar than the three first epochs. This 

 epoch, which is also called the ceenolithic or csenozoic 

 epoch, extended from the end of the cretaceous system to 

 the end of the pliocene system. The strata deposited 

 during it amount only to a thickness of about 3000 feet, and 

 consequently are much inferior to the three first great 

 groups. The three systems also into which the tertiary 

 period is subdivided are very difficult to distinguish from 

 one another. The oldest of them is called eocene, or old 

 tertiary ; the newer miocene, or mid tertiary ; and the last 

 is the pliocene, or later tertiary system. 



The whole population of the tertiary epoch approaches 

 much nearer, on the whole as well as in detail, to that of 

 the present time than is the case in the preceding epochs. 

 From this time the class of Mammals greatly predominates 

 over all other vertebrate animals. In like manner, in the 

 vegetable kingdom, the group — so rich in forms — of the 

 Angiosperm^s, or plants with covered seeds, predominates, 

 and its leafy forests constitute the characteristic feature 

 of the tertiary epoch. The group of the Angiosperms con- 

 sists of the two classes of single-seed-lobed plants, or Mono- 

 cotyledons, and the double-seed-lobed plants, or Dicotyledons. 

 Tlie Angiosperms of both classes had, it is true, made their 

 appearance in the Cretaceous period, and mammals had 

 already occurred in the Jurassic period, and even in the 

 Triassic period ; but both groups, the mammals and the 

 plants with enclosed seeds, did not attain their peculiar 

 development and supremacy until the tertiary epoch, so 

 that it may justly be called after them. 



The fifth and last ma,in division of the organic history 



