216 ZOOLOGICAL GEOGRAPHY. [part hi. 



Ill — The Siberian Sub-region, or Northern Asia. 



This large and comparatively little-known subdivision of the 

 Palrearctic region, extends from the Caspian Sea to Kamschatka 

 and Behring's Straits, a distance of about 4,000 miles ; and 

 from the shores of the Arctic Ocean to the high Himalayas of 

 Sikhim in North Latitude 29°, on the same parallel as Delhi. 

 To the east of the Caspian Sea and the Ural Mountains is a great 

 extent of lowland which is continued round the northern coast, 

 becoming narrower as it approaches the East Cape. Beyond 

 this, in a general E.KE. direction, rise hills and uplands, soon 

 becoming lofty mountains, which extend in an unbroken line 

 from the Hindu Koosh, through the Thian Shan, Altai and 

 Yablonoi Mountains, to the Stanovoi range in the north-eastern 

 extremity of Asia. South of this region is a great central basin, 

 which is almost wholly desert ; beyond which again is the vast 

 plateau of Thibet, with the Kuenlun, Karakorum, and Hima- 

 layan snow-capped ranges, forming the most extensive elevated 

 district on the globe. 



The superficial aspects of this vast territory, as determined by 

 its vegetable covering, are very striking and well contrasted. A 

 broad tract on the northern coast, varying from 150 to 300 and 

 even 500 miles wide, is occupied by the Tundras or barrens, 

 where nothing grows but mosses and the dwarfest Arctic plants, 

 and where the ground is permanently frozen to a great depth. 

 This tract has its greatest southern extension between the rivers 

 Obi and Yenesi, where it reaches the parallel of 60° north lati- 

 tude. Next to this comes a vast extent of northern forests, 

 mostly of conifers in the more northern and lofty situations, 

 while deciduous trees preponderate in the southern portions and 

 in the more sheltered valleys. The greatest extension of this 

 forest region is north of Lake Baikal, where it is more than 

 1,200 miles wide. These forests extend along the mountain 

 ranges to join those of the Hindu Koosh. South of the forests 

 the remainder of the sub-region consists of open pasture-lands 

 and vast intervening deserts, of which the Gobi, and those of 

 Turkestan between the Aral and Balkash lakes, are the most 



