LIFE-ZONES 627 



of many Siberian and Mongolian species overlap. The Turgun 

 Range, for instance, is more truly Mongolian than the Tannu- 

 ola. This forms the northern limit of the yak ; it is here we 

 first meet with the ovis amnion, — although it formerly ranged 

 on to the southern slopes of the Tannu-ola; here, too, begin the 

 snow-leopard, the marmot, and the snow-cock. Siberian types 

 are represented by the ptarmigan {Lagopus rupestris), which 

 ranges thus far over the Tannu-ola. 



The Altai Range is difficult to define as belonging exclusively 

 to either faunistic zone ; but I should continue the line of de- 

 marcation, which runs the length of the Tannu-ola, along the 

 Little Altai and thence in a south-easterly direction along the 

 crest of the Great, or Mongolian Altai to the head-waters of the 

 Black Irtish. In other words, all that part of the Altai which 

 drains into the Arctic should belong to the Siberian, whilst the 

 remainder should represent a portion of the Mongolian zone. The 

 Urungu basin should probably be included in the former. Beyond 

 the Altai, in a south-westerly direction, lies the lowland of Dzun- 

 garia, which connects the plains of Siberia with the plateau 

 of Mongolia, and across which continues the line of demarcation 

 between the two main life-zones, as well as another secondary 

 line to show the subdivision between Altai — whether Mongolian 

 or Siberian — and Tian Shan fauna. 



The first and most important line, which we have so far traced 

 to a point on the crest of the Altai somewhere between the 

 sources of the Black Irtish and the Urungu rivers, now continues 

 across the central plains of Dzungaria, cuts in between the 

 mountain groups of Barlik and Urkashar on the south and the 

 Sair and Tarbagatai on the north ; and runs westwards into 

 Northern Turkestan. This line forms the southern limit of the 

 Siberian larch tree (Larix sihirica) and the northern limit of 

 the Chukar partridge {Caccahis chukar) and the Tian Shan spruce 

 {Abies schrenkiana). But most forms peculiar to the Tian Shan 

 area stop at the Ala-tau, and do not extend their range across 

 the Dzungarian depression, or Gate, to the Barlik Mountains. 



Practically the whole of Dzungaria belongs to the Central 

 Asian zone, which includes the subdivisions of the Tian Shan 

 and Mongolia. The plains form a neutral ground for some widely 



