162 THE GEOGRAPHY OF MAMMALS 



American inamrnals, first of all excludes from what he 

 terms the North American Region the extreme northern 

 parts of that continent. He considers that the Arctic 

 portion of that continent, namely, that beyond the limit 

 of arboreal vegetation, forms, together with the similar 

 part of the Old World, a separate Region, or, as he terms 

 it, " the Arctic Realm." 



Furthermore, the southern part of North America 

 south of the Mexican tableland, together with the low- 

 lying country of Mexico on either flank, he assigns to the 

 American Tropical Realm. The remainder of the con- 

 tinent, combined with the great mass of Europe and Asia, 

 forms, according to this author, the North Temperate 

 Realm. This scheme of division does not differ essentially 

 from that of Mr. Allen. The Arctic portion of North 

 America forms, no doubt, as Mr. Allen puts it, " part of a 

 homogeneous hyperborean faunal area of circumpolar 

 distribution." 



Mr. Allen's American Tropical Realm has already been 

 treated of in the chapter of this volume dealing with the 

 Neotropical Region (see p. 52). There remains, therefore, Mr. 

 Allen's North American Region, which nearly corresponds 

 to the Nearctic Region of our scheme of classification. Mr. 

 Allen divides his North American Region into two Sub- 

 regions — the Cold Temperate and the Warm Temperate, 

 the two latter falling into two provinces, a Humid or 

 Eastern and an Arid or Western. Proceeding further, he 

 divides the Humid province into two sub-provinces, namely, 

 an Apalachian or Northern and an Austro-riparian or 

 Southern. The Arid or Western province is also separated 

 into two sub-provinces — the Campestrian or Northern and 

 the Sonoran or Southern, and, besides this, the sub- 



