DISTRIBUTION OF MAMMALS. 337 



northward extension of tropical life which inhabited this region dur- 

 ing the middle and later portions of the Tertiary Period and in the 

 Quaternary. 



Divisions of the North Temperate Realm. The North Temperate 

 Eealm is primarily divisible in two directions, giving in each two re- 

 gions, namely, (1) by a longitudinal division into (a) a North American 

 Region and (6) a Europceo- Asiatic Region; and (2) latitudinally, into 

 (a) a Cold Temperate and (&) a Warm Temperate Region. The Cold 

 Temperate, if limited on both continents by the isotherm of 36 F., 

 presents a nearly uniform fauna throughout, its southern limit in both 

 corresponding with the natural (that is, before modified by human 

 agency) southern limit of distribution of Tarandus and Alces. While 

 there is at this point in North America a well-marked transition in the 

 fauna, the change in Europe and Asia appears to be less marked, the* 

 first important transition in the Old World being much farther south- 

 ward, even as low almost as the isotherm of 60 F. Hence the divisions 

 of the Temperate Realm in the Old World partake of the nature of 

 temperate and subtropical rather than cold-temperate and warm-tem- 

 perate. Here, in consequence of the great elevation and extent of the 

 Himalayan Plateau, the northern or temperate division is greatly nar- 

 rowed in Central Asia, where it becomes, according to Mr. Wallace, 

 almost wholly separated info two quite widely detached regions, namely, 

 the u Mediterranean " and " Mauchurian Subregions n . 



As thus divided, the temperate and subtropical divisions of the Old 

 World are very strongly marked. The latter consists mainly bf North- 

 ern Africa, Asia Minor, Persia, Afghanistan and Beloochistan, North- 

 ern China, and Manchuria, with barely a narrow belt along the Medi- 

 terranean coast of Europe and the Spanish Peninsula. As already 

 stated, it is strongly tinged with tropical forms. While there is a 

 general prevalence of temperate types, we meet also with the large and 

 essentially tropical forms of Felis, several Monkeys, several species of 

 Viverridce, Hycena, ffystrix, Equus, and other distinctively tropical or 

 subtropical types. The northern or temperate division of the Europseo- 

 Asiatic Region seems to constitute two well-marked provinces, the one 

 Eastern or European, the other Western or Asiatic. The former cor- 

 responds with Mr. Wallace's " European Subregion ", exclusive of its 

 northern third; the latter with his "Siberian Subregion", exclusive 

 likewise of its boreal portion. For the southern or subtropical division 

 I adopt the subdivisions proposed by Mr. Wallace, with, for the present, 

 the boundaries he has assigned them, namely, a Western or Mediter- 

 ranean Province and an Eastern or Manchurian Province. These two 

 provinces, as already noted, are quite widely separated, in conse- 

 quence of the southward extension of the cold-temperate fauna over 

 the Thibetan plateau to the Himalayas. The fauna of the Thibetan 

 plateau is said by Mr. Blandford to be " essentially Boreal, Alpine and 

 even Arctic types prevailing, the country having in many parts a cli- 



