346 



BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



feature is hence an approximately equal blending of temperate and 

 tropical forms, whose respective habitats here overlap. Many of the 

 northern forms do not quite reach the southern limit of the region, just 

 as many of the southern forms do not quite reach its northern limit. It 

 is distinguished from the North American Temperate Eegion by the 

 preponderance of tropical life, and from the Brazilian Eegion by the 

 copious intermingling therewith of northern forms, an element wholly 

 lacking in the Brazilian Eegion. 



Genera of the Central American Region. 



8um)nary. 



Whole number of genera 63 



Peculiar or mainly limited to the region 6 



Occurring also over most of the Brazilian Region 40 



Occurring also over much of the North American Region 24 



Occurring also over most of both North and. South America, but not in the Old 



World 5 



Subcosmopolitan 8 



Tropicopolitan 2 



Antillean Eegion. — The Antillean Eegion differs from both the Cen- 

 tral American and Brazilian most strongly in negative characters — 

 through what it lacks rather than in what it has— although it pos- 

 sesses a number of peculiar genera. The Chiroptera form two-thirds of 

 the genera and not less than five-sixths of the species. Of the eight 

 peculiar genera, five are Bats, the others being Solenodon (the only In- 

 sectivore), Capromys, and the closely allied Plagiodonta, which together 



