876 PHYLUM CHORDATA I CLASS MAMMALIA 



from the wall of the abdomen, but is usually retractile. 

 There is a bicornuate uterus. Several and usually many 

 offspring are born at once. 



The allantoic placenta is discoidal and deciduate. There 

 is a provisional yolk-sac placenta. 



Insectivora are represented in the temperate and tropical 

 zones of both hemispheres, but not in S. America (except 

 in the Northern Andes) nor Australia. In the former 

 continent their place is taken by the insectivorous opossums. 



Examples. — The hedgehogs {Erinaceus), throughout Europe, Africa, 



and most of Asia, dentition ^^^ ; the shrews {Sorex), in 



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Europe, Asia, and N. America, dentition -^ ; the moles (Talpa), 



throughout the Palsearctic region ; the tailless tenrec {Centeles) 

 of Madagascar ; the S. African golden moles {Chrysochloris), 

 probably the most primitive of all Eutheria ; the African jumping 

 shrew (Macroscelides) ; the Oriental tree-shrews (Tupaia). 



Gai.eopithecid^ 



Some authorities make a separate order for the very divergent 

 Galeopithecus, from the Malay Archipelago and the Philippines. They 

 are arboreal vegetarian animals. The fore- and hind-hmbs are 

 connected by a parachute, and the animals can glide from tree to 

 tree, " sometimes traversing a space of seventy yards with a descent 

 of only about one in five." The structure of the incisors is unique 

 among Mammals. They are expanded laterally, compressed from 

 before backwards, and furnished with many cusps. The lower 

 are pectinated, the flattened crowns being penetrated by numerous 

 vertical slits, and the outer of the two upper pairs have double roots. 



The dentition is ^^. The molars are multicuspidate. The orbit 

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has an almost complete bony ring. There is a tympanic bulla. The 

 cerebral hemispheres have a few furrows. There is a simple stomach 

 and a large sacculated caecum. The testes are scrotal, the penis 

 pendulous. There are two paurs of pectoral mammae, and one young 

 one at a birth. 



Order Chiroptera. Bats 



Bats are specialised Mammals related to Insectivores. 

 They have the power of flight, the fore-limbs being modified 

 as wings. The wing is formed by a fold of skin which 

 usually begins from the shoulder, extends along the upper 

 margin of the arm to the base of the thumb, thence between 

 the long fingers, and along the sides of the body to the hind- 

 legs or even to the tail. Contrasted with the wing of a 



