Tropical Mammals. ?>3 



Arvicola pallidus Perognathus fasciatus 

 Symtptoniys rooperi olivaceous 



Lepus americanus Virginian us Putorius nigripes * 



eampestrie Vulpes velox 



idahoensis * Scapanus americanus 



sylvaticus nuttalli * Vespertilio melanorhinus 



Local elevations of the land in the Sonoran Region are capped 

 with isolated patches of Transition or Boreal species, according 

 to the temperature to which their summits attain ; and if the 

 elevation is sufficient to secure a Boreal fauna and flora the lat- 

 ter is always separated from the Sonoran of the surrounding 

 plane by a belt or girdle of Transition Zone forms. 



The TROPICAL REGION reaches the United States at two remote 

 points Florida and Texas. In the former it exists as a narrow- 

 subtropical belt encircling the southern half of the Peninsula 

 from Cape Malabar on the east to Tampa Bay on the west. In 

 Texas it crosses the Lower Rio Grande from Mexico and extends 

 north to the neighborhood of the Nueces River. In western 

 Mexico the Tropical Region reaches Mazatlan. 



Fourteen families of Tropical mammals inhabit North Amer- 

 ica north of Panama, namely : 



Didelphidae DasyproctidcT 



Bradypodidse Procyonidse 



Myrmecophagida? Solenodontidse 



Dasypodidre Emballonurida? 



Dicotylida? Phylloetomatidpe 



Tapiridse Hapalidae 



Octodontidse Cebidre 



Of the above fourteen families, six reach the United States, 

 namely, Didelphidse, Dasypodidae, Dicotylidve, Procyonidw, Embal- 

 InimrldtP) and Phyllostomatidde,, and two of the latter (Diddphidse 

 and Procyonidse) penetrate the entire breadth of the Sonoran 

 Region, the Procyonidse even entering the low r er edge of the Boreal. 

 Descending from families to genera, it is found that no less than 

 02 tropical genera of non-pelagic mammals inhabit North 

 America north of Panama, of which number 9 enter the United 

 States from Mexico, namely, Didelphis, Tatusia. Dicotyles, Nasuci, 

 Procyon, Felis, Molossm, Nyctinomus, and Otojpierw. Of these, 

 Didelphis, Fells, and Procyon now reach considerably further 

 north than the others, as just pointed out in speaking of the 



* Range down into Upper Sonoran also. 



* f>-Bioi,. So.'., WASH., Vor,. VII, lS!f_>. 



