LATEK LIFE ON THE EAKTH 57 



as well as some sub-orders which are now extinct. 

 In the Oligocene we find some existing genera, and 

 many more in the Miocene. The extinct sub-orders 

 are chiefly from North America, and are generalised 

 groups connecting the existing orders. They had 

 very small brains and smooth bones without ridges ; 

 all had five toes on each foot, and their molar teeth 

 were trituberculate. 



Probably the insectivora are the earliest of the 

 Eutheria, and they gave rise to three larger and two 

 smaller branches. The larger branches are, first, 

 the herbivorous animals, whose chief food is leaves 

 and young shoots of trees, the canine teeth are small 

 or absent, and the molars usually have the enamel 

 folded and with cement between the folds. The 

 toes have hoofs or blunt claws. This branch sub- 

 divided into several smaller ones, one of which the 

 sea-cows is aquatic. The second great branch is 

 the carnivorous animals, living on other vertebrates. 

 They have large canine teeth and sharp claws. 

 There are two aquatic sub-branches, the seals and 

 the whales. The third branch is the Quadrumana 

 or Primates, which are arboreal, and whose princi- 

 pal food is fruit, but they are more or less omni- 

 vorous. 



The two lesser branches from the insectivora are 

 the bats and the edentata, the latter having no 

 enamel on their teeth, but large claws- for digging. 



The Eocene Creodonta are the primitive Carni- 

 vora ; but they had no canine teeth , and in their 

 dentition they are related to both the Insectivora 

 and the polyprotodont marsupials. With them were 



