DISTRIBUTION OF ANIMAL LIFE. 359 



World. They are distributed into 32 species, 19 of which 

 belong to America. The Edentata, therefore, do not form 

 more than one- fiftieth of the Mammalia. 



The Pachydermata, which owe their name to the thickness 

 of their skin or hide, almost exclusively belong to the Old 

 World. None are found in Australia. The number of their 

 species is 38, of which 5 only belong to Southern and Central 

 America. The Pachyderms form, therefore, nearly one-thirty- 

 seventh of the Mammalia. 



The Cetacece, which the naturalists of antiquity ranked 

 among the fishes, though the females bear their young alive, 

 and are furnished with a mammary apparatus, chiefly frequent 

 the Northern waters, but some of their species are found in 

 the South Pacific. They represent, it may be assumed, about 

 a one-hundredth part of the Mammalia. 



The JBirds, by their feather-clad bodies, and by the trans- 

 formation of their two fore-limbs into wings, form the best- 

 characterised class in the whole animal kingdom. But natur- 

 alists can no more agree as to the number of their species 

 than as to the number of species composing the Mammalia. 

 Some, taking as a foundation the rich ornithological collection 

 in the Berlin Museum, allow for 6000 species being distributed 

 over the surface of the globe ; others, like Lessen, increase the 

 total to 6266 ; while Dr Gray, no mean authority, raises it to 

 at least 8000. 



