874 PHYLUM CHORDATA : CLASS MAMMALIA 



There is a small external ear. The testes lie in an external 

 scrotum. 



The sea-lion Otaria, ^^^^~ , Pacific and S. Temperate seas. 



2, I, 4, I 



Family Trichechidaj — Walruses, intermediate between the Otariidae 

 and the seals. The hind-feet can be turned forwards and used 

 on land. The upper canines form large tusks ; the other teeth 

 are small, single rooted, and apt to fall out ; those generally in 



use are , but the dentition of the foetiis is ^-^-. 

 0130 3131 



The jaw seems relativeh short, an adaptation perhaps to mussel- 

 crushing instead of fish-catching. 

 There are no external ears. 

 The walrus or morse, Trichechtis (Arctic). 

 Family Phocidae — Seals, the most specialised Pinnipeds. The hind- 

 limbs are stretched out behind, and the strange jumping move- 

 ments on land are effected by the trunk, sometimes helped by 

 the fore-limbs. The palms and soles are hairy. There are well- 

 developed canines ; the upper incisors have pointed crowns ; 



there are - back teeth. There is no external ear. The testes 



5 

 are abdominal. 



The common seal {Phoca), ^^^, the grey seal (Halichoerus), 



the monk seal [Monachus), the large elephant seal {Macrorhinus 

 leoninus). 



Order Insectivora 



This order includes hedgehog, mole, shrews, and related 

 Mammals usually of small size. There is much diversity 

 of type, so that a statement of general characters is very 

 difficult. 



Most Insectivores run about on the earth ; the mole 

 (Talpa), and others like it, are burrowers ; Potamogale, 

 Myogale, and others are aquatic ; Tupaia and its relatives 

 live like squirrels among the branches. 



Most feed on insects ; some arboreal forms eat leaves 

 as well ; the moles eat worms ; Potamogale is said to feed 

 on fish. 



The body is usually covered with soft fur, but the hedge- 

 hog [Erinaceiis) is spiny, and so to a less extent is Centetes, 

 the ground-hog of Madagascar. The digits, usually five in 

 number, are clawed, and the animals walk in plantigrade 

 or semi-plantigrade fashion. In most, the mammae are 

 thoracic or abdominal. 



The cranial cavity is small ; the skull is never high ; the 



