72 THE GEOGRAPHY OF MAMMALS 



Section V. — The Central American Sub-region 



This Sub-region, as has been already shown, contains the 

 coast-lands of Mexico lying along the Pacific and Atlantic 

 shores from Mazatlan on the north on one side, and from 

 the Rio Grande on the other, together with the whole of 

 Central America from the Isthmus of Tehuantepec to that 

 of Panama. 



As regards the fauna of this part of America, we are 

 fortunate in being able to refer to the excellent account of 

 it contained in the " Biologia Centrali- Americana " of Messrs. 

 Salvin and Godman. The volume relating to the 

 mammals in this work was undertaken by Mr. Alston, and 

 finally completed after his death by one of the authors of 

 this work in 1882 (3). Out of a total of sixty- nine genera 

 of mammals represented in this Sub-region, only two seem 

 to be absolutely restricted to it, and these, moreover, are 

 genera of bats, which may possibly be found at some future 

 time to extend into the main South American continent. 



Of the sixty-seven non - peculiar Central - American 

 genera of mammals, forty-one are Neotropical types — 

 that is, found also in one or more of the other Sub-regions 

 of this Region — five are Nearctic, nine are found both in 

 the Nearctic and in other Sub-regions of the Neotropical 

 Region, and twelve are cosmopolitan, or, at any rate, found 

 in some part of the Old World as well as in the New. 



These facts show conclusively the thoroughly Neo- 

 tropical character of the Central-American Sub-region, 

 which, although the admixture of northern forms has 

 really made very little progress, may be defined as that 

 part of the Neotropical Region which has been subjected 

 to an incursion of Nearctic types. 



