2 THE GEOGRAPHY OF MAMMALS 



geography, and consider how the earth's surface may be 

 most naturally divided into Primary Regions, taking the 

 amount of similarity and dissimilarity of animal life as 

 our sole guide. In order to endeavour to solve this 

 problem, let us select the mammals, as the most highly 

 organised and altogether the best-known group of the 

 animal kingdom, and examine the geographical distribu- 

 tion of this class of animals over the world's surface. 



Mammals are divided by naturalists into eleven large 

 groups, called " Orders." As regards their distribution, 

 however, these Orders fall into two very different categories, 

 according as they live on land or in the water — terrestrial 

 and marine. For out of the eleven Orders, one of the 

 principal divisions of the Carnivora — the Pinnipeds or 

 seals, and two other Orders in their entirety — (the Cetaceans 

 or whales, and the Sirenians or Manatees) are specially 

 adapted for existence in water. Land is, therefore, a barrier 

 to their extension, whereas, on the contrary, in the case of 

 the ordinary terrestrial mammals, land is the means by 

 which they extend their ranges, and seas and rivers form 

 their restraining boundaries. 



We will for the present put aside the marine mammals, 

 and address ourselves to the discussion of the distribution 

 of the nine terrestrial Orders, namely : — 



1. Primates. 6. Ungulata. 



2. Chiroptera. 7. Edentata. 



3. Insectivora. 8. Marsupialia. 



4. Carnivora. 9. Monotremata. 



5. Kodentia. 



Now, as is generally agreed by naturalists, one of the 

 most certain and best ascertained points in the classifica- 

 tion of mammals is, that these nine Orders can be grouped 



