Chap, in.] MAMMALIA. ' 99 



the primitive type, that they are without true 

 teeth. 



B. Metatheria (Didelphia). These are the 

 Marsupials; they have true teats, but no placenta ; 

 the epipufoes are large, but the coracoicl rudimen- 

 tary. The Marsupials exhibit a great range of varia- 

 tion and structure among themselves ; some are car- 

 nivorous, like the Opossum, the Dasyurus, and the 

 Thylacine ; others herbivorous, like the kangaroo 

 (Macropus) and the wombat (Phascolomys). 



C. Eutheria (Monodelphia). Here stand the 

 rest of the Mammalia, which, without any known 

 exception, have teats, a placenta, rudimentary or 

 no epiptifoes, and a rudimentary coracoid. The 

 least differentiated are the Insectivora (e.g. hedgehog, 

 mole), to which are most closely allied the Chiroptera 

 (bats), and the Rodents (rat, rabbit) ; in these the 

 yolk sac takes a larger share in the formation of the 

 placenta than it does in other mammals. 



The Edentata form, at the present day, an isolated 

 group, represented by the sloths, anteaters, and arma- 

 dillos, by the pangolins (Manis), and by the ant-bear 

 (Orycteropus). The hoofed animals, or Ungfulata, 

 form a well-marked division, in which the group of 

 the even-toed forms (Aitiodactyla), such as the 

 pig, deer, and cow, is very distinct from that of the 

 odd-toed (Perissodactyla), such as the tapir, rhino- 

 ceros, and horse. With the Ungulata, the coney 

 (Hyrax) and the elephant may be associated (Flower). 

 Of aquatic forms, the Cetacea, or porpoises, toothed 

 whales, and whalebone whales seem to stand nearest 

 to the Ungulates. Of the affinities of the other 

 aquatic mammals, the Sirenia, or manatee and 

 dugong, we can only with confidence say that they 

 are not with the Cetacea. The true Carnivora are 

 the dogs, cats, and bears, and with these are closely 

 allied the walruses and seals. 



