INSECTIVORA. 757 



The jaw seems relatively 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 are 



5 



abdominal. 



The common seal (Phoca], , the grey seal (Halichcerus), 



2I&I 



the monk seal (Monachiu;), the large elephant seal (Macrarhinus 

 Icon inns}. 



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 (Erwaceiis) is spiny, and so to a less extent is Centetes, 

 the groundhog 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 

 facial region is long ; the zygomatic arch is slender or 

 incomplete. Except in Potamogale^ there are clavicles. 



There are never fewer than two pairs of lower incisors. 

 The enamelled molars have tuberculated crowns and well- 

 developed roots. In many cases it is not easy to distinguish 

 the usual division of the teeth into incisors, canines, pre- 

 molars, and molars, but in many the dentition is typical- 



3> '. 4, 3 = 44- 



In the hedgehog, according to Leche, i. 3, pm. 2, m. 1-3, 



