RESULTS OF THE EXPEDITION. 
159 
of northern and southern Asiatic forms, central Asia 
possesses a distinct resident avi-fauna, probably somewhat 
limited in extent, but doubtless altogether inadequately- 
represented by the few forms as yet discovered. 
With the birds of Siberia and the Amoor Land the 
writings of Pallas, Middendorf, Von Schrenk, and E-adde, 
have made us fairly acquainted ; while those of India, from 
the sea to the borders of Chinese Tartary and Thibet, have 
been, I believe with the exception of some small Grass- 
Warblers, or rare stragglers, for the most part recorded. 
Many Siberian and Indian species are identical, birds that 
inhabit the one country during one part of the year, straying 
or regularly migrating at other seasons into the nearest 
portions of the other ; many of these also occur as might 
have been expected in Yarkand. Several of our species 
that do not find their way so far north as Siberia, resort to 
Yarkand for the summer, or possibly in some cases reside 
there permanently, while one at least of the more northern 
forms that never go so far south as the Himalayas finds 
even during the hot season a home in that country ; but 
over and above these we have traces of a distinct and local 
avi-fauna which neither in summer extends to Siberia, nor 
in winter to the mountains even of India. 
It may be thought that the limited number of the 
peculiar Yarkand species as yet discovered scarcely warrants 
a belief in the existence of a distinct Central Asiatic avi- 
fauna, but if the very small area actually explored be borne 
in mind, as also the fact that few as were the species 
observed, more than one tenth of these are unknown to 
both the northern and southern sections of the continent, I 
think it will be admitted that the conclusion is not altogether 
unreasonable. 
Europe presents us with no parallel case ; it would be 
impossible, probably, to point to any district in that 
continent inhabited by even six peculiar bond-fide . sipecies, 
which occur neither to the north or south ; but in Africa it 
appears to me that we find a somewhat similar region 
possessing likewise a peculiar avi-fauna — an elevated 
tableland, much of it a perfect desert, hemmed in by 
