Tropical Mammals. 33 



Arvii'ola pallidas Terognathus fasciatus 

 Synaptomys cooperi olivaceous 



Lepiis americanus virginiunns Putorius nigripes * 



campestris Vulpes velox 



idahoensis * Soapanus americanus 



sylvaticus nuttalli * Vespevtilio 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 Ijy 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 neighljorhood of the Nueces River. In western 

 Mexico the Tropical Region reaches INIazatlan. 



Fourteen families of Tropical mammals inhabit North Amer- 

 ica north of Panama, namely : 



Didelphida? Dasyproctidfe 



Bradypodidpe Procyonidse 



Myrmecophagid?e Solenodontida? 



Dasypodidfe Eniballonurida' 



Dicotylid;e Phyllostomatidie 



Tapii-ida? Hapalidte 



Octodontida? Cebida^ 



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

 namely, DidelphldR', Dasypodidx, Dkotylidx, Procyonkhv, Emhal- 

 loiuirldiTe, and PhijllostomatidcV, and two of the latter (Didelpli'uhr 

 and Procyonidx) penetrate the entire breadth of the Sonoran 

 Region, the Proryoiildse even entering the lower edge of the Boreal. 

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

 62 tropical genera of non-pelagic mammals inhabit North 

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

 States from Mexico, namely, Didelphis, Tatiisia, Dkotyles, Nasua, 

 Procyon, Fells, Molussus, Nydiiiomus, and Otopterus. Of these, 

 Duhlpkis, Feli% and Procyon now reach considerably further 

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



* Range down into Upper Ronoran also. 



.-)-Hioi.. Soi-.. Wash., Veil.. VII, 1892. 



