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ZOOLOGICAL GEOGRAPHY. 
[part hi. 
III. — The Siberian Sub- region, or Northern Asia. 
This large and comparatively little-known subdivision of the 
Palaearctic 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.N.E. 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 
