16 Mammals of Eastern Asia 
mountains thrusting eastsoutheast from Yunnan are even lower, 
falling from 6000 feet in western Kweichow to 1000 or less in 
the east of that province. They separate the West or Si-kiang 
River from the South China Sea. A low spur of this system, 
interrupted by the Hainan Strait, is continued as the 6000-foot 
mountains on Hainan Island. 
At least three more systems of mountains originate from the 
southward-projecting spurs of the east Tibetan Mountains 
where four huge rivers, some in canyons 2 miles deep, flow 
through an area only some 200 miles across. The great divide 
between the Mekong and Salween Rivers expands at its south- 
ern end into the high hill country, 6000 to 8000 feet, of extreme 
northern Siam. These ranges continue through Tenasserim into 
the hilly northern Malay Peninsula and reappear in the lower 
peninsula as the isolated hills of Kedah and Perak. From the 
Tibetan Plateau just west of the upper Chindwin the Namkiu 
Range forks about the source of the Irrawaddy River, the 
eastern fork extending as gradually lowering ridges, 3000 to 
4000 feet, south through the Shan States almost to Pegu and 
Rangoon. The west fork expands greatly into the Kachin Hills, 
the Lushai Hills, the Chin Hills, and Arakan Yoma Range, of 
eastern Bengal, Assam, and Arakan. This last great mass of 
hills — particularly the Patkoi, Naga, Jaintia, the Khasi Hills, 
from 8000 to 12,000 feet high — forms the southern edge of 
the valley of the mighty Brahmaputra River south of its point 
of emergence from the interior of the Himalayas. 
The Tibetan Plateau in combination with the Himalayas can 
be compared to the handle of a gigantic fan, with radial moun- 
tain systems and the great rivers between them diverging to the 
east and south like the ribs. 
Swamps, Lakes, and Deserts. Swampy areas of large size 
are absent except about the courses and deltas of some of the 
rivers. The most important areas of swamp are along the Ningpo 
and the Yangtse Rivers in China, the lower portions of the 
