DISTRIBUTION OF MAMMALS 167 



the population of the islands, are three: Asia, America, and 

 Australia. The last, though technically an island, is so large 

 and has been occupied by its specialized marsupial fauna for so 

 long a period that it is conveniently treated as a third continent. 

 Asia, particularly the East Indies, has greatly out-distanced 

 Australia and the Americas in providing fauna! elements for the 

 population of the islands. The Americas, on the contrary, have 

 provided but a handful of land-dwelling species, most of these 

 reaching islands rather near the American coast and only one 

 of them going as far as Hawaii. A few representatives of the 

 great evolutionary outburst of marsupials in Australia and 

 New Guinea have reached Talaut, Celebes, the easternmost 

 Lesser Sundas, and the Solomons. 



The Aleutian Islands, included in the Holarctic Region, have 

 a mammal fauna that decreases from the Alaskan end of the 

 chain westward. The first island, Unimak, separated from the 

 Alaska Peninsula by a shallow, narrow strait, has almost all of 

 the mammals that occur on the treeless part of the peninsula. 

 Some species have not yet been recorded, but this is probably 

 because of inadequate collecting. The islands west of Umnak, 

 which is itself one hundred and forty miles west of Unimak, may 

 have no native land mammals. Caribou, bear, Arctic fox, wolf, 

 wolverine, mink, weasel, the Arctic hare, marmot, ground squir- 

 rel, lemming mouse and lemmings, and a water shrew (Sorex) 

 may occur on the landward islands ; these are all North Ameri- 

 can forms, but they have close relatives in northern Asia. 



The Kurile Islands similarly have a limited mammal fauna, 

 chiefly species common to both Old and New Worlds. The arctic 

 fox, red fox, brown bear, pygmy weasel, red-toothed shrew, 

 varying hare, and a mouse-eared bat are such forms, but the 

 wood mouse and the long-eared bat (Plecotus) occur only in 

 the Old World Palearctic Subregion. 



Japan, too, has a fauna consisting chiefly of local forms of 

 northern continental groups — various bats, bears, the red fox, 

 wolf, varying hare, pika, chipmunk, meadow mouse or vole, and 



