74 DISTRIBUTION OF MAMMALS. [CH. II 



whereby the facts of distribution may be at once and with 

 ease appreciated. 



Mr Sclater founded his regions mainly upon the dis- 

 tribution of Passerine birds; but in a subsequent lecture 1 

 upon the geographical distribution of the Mammalia he 

 applied the same regions for the purposes of tabulating 

 the distribution of that group of animals also. In 

 considering the distribution of the existing Mammalia 

 four salient facts are at once apparent. 



(1) Australia has both Monotremes and Marsupials. 



(2) America has Marsupials but no Monotremes. 



(3) The remainder of the world has Monodelphian 

 Mammals only. 



(4) New Zealand has no Mammals at all. 



On this basis Mr Sclater divided the world as follows : 



I. Land where Monodelphs only occur ; no Marsupials 

 or Monotremes. Europe, Asia, Africa, Asiatic islands 

 down to Wallace's line, North America 2 . This land may 

 be called Arctogcea. 



II. Land where Monodelphs and Marsupials occur; 

 no Monotremes. America south of the Isthmus of 

 Tehuantepec. This land may be called Dendrogcea. 



III. Land where Marsupials prevail ; no Monodelphs 

 but rodents and bats; Monotremes. Australia. This 

 may be called Antarctogcea. 



IV. Land without Mammals (except bats) 3 . New 



1 "The Geographical Distribution of Mammals." Science Lectures 

 for the People, 1874. 



2 The common Opossum ranges however into this region. 



3 For a possible exception see below. 



