634 



MAMMALIA. 



On the other side we place the great series of Carnivora, 

 such as cats, dogs, bears, and seals. Beside these may be 

 ranked the Insectivora, such as hedgehog, mole, and shrew, 

 and the bats or Chiroptera, which seem to be specialised 

 Insectivores. 



In the middle we place the series which, beginning with 

 the Lemurs, leads through various grades of monkeys to a 

 climax in man. Among the monkeys are the small and 

 simple marmosets, the flat-nosed American monkeys, the 

 dog-like apes of the Old World, and the anthropoid apes, 

 which most nearly approach ourselves. 



But it must be carefully noted that these orders are often 

 linked by extinct types. Thus, to take one instance only, it 

 is believed by some that the extinct Phenacodus has affinities 

 with Ungulates, Carnivores, and Lemurs. 



We may summarise our general classification thus : 



MAN 



and 



MON KEYS 



UNGU 



\ 



LATES 



LEM 



URS 



RODENTS 



CAR NIVORES 

 BATS 



INSECTIVORES 



CETACEANS 



EXTINCT SYNTHETIC TYPES 



SIRENIA 



EDENTATA 



MARSUPIALS 



MONOTREMES 



GENERAL CHARACTERS. All Mammals are quadrupeds, 

 except the Cetaceans and Sirenians, in which the hind limbs 

 have disappeared, leaving at most internal vestiges. There is 

 generally a distinct neck between the head and the trunk, and 

 the vertebral column is, in most cases, prolonged into a tail. 



Hairs are never entirely absent. In most they form a thick 

 covering, but they are scanty in Sirenians and in the hippo- 



