66 THE GEOGRAPHY OF MAMMALS 



a very well-marked Sub-region, in which the terrestrial 

 mammals, though not very numerous, nearly all belong 

 to peculiar genera. 



The higher ranges of the Andes from Ecuador south- 

 wards, together with the pampas of Southern Argentina 

 and Patagonia, form another well-marked Sub-region char- 

 acterised by a number of peculiar genera and species. 

 But the whole remainder of the Neotropical Region from 

 Mexico to Southern Brazil contains, so far as we under- 

 stand it at present, a more or less homogeneous mammal- 

 fauna, of which, however, the northern half possesses a 

 considerable admixture of Nearctic forms, while the 

 southern preserves a more purely indigenous facies. It 

 will, therefore, be quite in accordance with the facts of 

 nature, as well as convenient, to separate the northern 

 portion of this extensive area as the Central American (or 

 Transpanamanic) Sub-region. But as regards the southern 

 portion, until our knowledge of the distribution of South 

 American mammals has made greater progress, it seems 

 best to unite the Colombian, Amazonian, and Brazilian Sub- 

 regions of the Ornithologists into one combined Sub-region, 

 which may be called the Guiano-Brazilian Sub-region. 



We shall thus have, as regards Mammals, four Sub- 

 regions of the Neotropical Region, as follows (see Map, 

 Plate III., p. 82) :— 



1. The Antillean Sub-region, comprising the whole of 

 the West India Islands except Curacao, Trinidad, and 

 Tobago. . 



2. The Central-American Sub-region, comprising the 

 low-lying and southern parts of Mexico and Central 

 America as far as the Isthmus of Panama. 



3. The Guiano-Brazilian Sub-region, comprising the 



