334 GEOGRAPHICAL DISTRIBUTION 
Since, as above indicated, the avifauna of the Nearctic Sub- 
region shews its intimate connexion with that of the Palearctic by 
the yearly interchange that obtains between Alaska and the north- 
eastern portion of Asia, it would seem most fitting to begin the 
consideration of the Palzarctic Subregion at that part of it. As 
in the Nearctic Subregion difficulty was found in defining the 
limits of its several Provinces, so there is difficulty here, and 
perhaps it is even greater in this far vaster area. The very fulness 
of details we possess in regard to some of the countries of our own 
Subregion, those of its western or European portion especially, 
makes the scarcity of information in respect of others all the more 
conspicuous, and renders comparison useless. In the eastern 
portion, its southern frontier cannot be as yet determined. Grant- 
ing that it includes the whole of Japan, the line of demarcation on 
the continent is open to much doubt: Mr. Wallace would place its 
commencement about Ningpo, just to the southward of Chusan, 
whence it would have to enclose the basin of the Yang-tse-Kiang, 
and then turn suddenly northward to skirt the valleys of the rivers 
which drain Cochin China, Siam, and Burma, as they undoubtedly 
belong to the Indian Region. Thence it would make for the 
eastern end of the Himalayas, on reaching which its course becomes 
fairly plain so far as the Hindoo Koosh; here it trends to the 
southward to include Afghanistan and the greater part if not 
the whole of Beloochistan. Skirting the northern shore of the 
Persian Gulf, it continues westward, passing to the north of Arabia, 
but comprising Mesopotamia and Palestine, with a remarkable 
exception to be presently noticed, and reaching the south-eastern 
corner of the Mediterranean Sea. Here its land-boundary is inter- 
rupted, but it may be taken up again in Tunis, if not in Tripoli, 
and, including all the ancient Mauritania—that is, the portion of 
Africa north of the Great Desert—meets the Atlantic Ocean about 
Mogador. The Subregion includes the Atlantic Islands (Canaries, 
Madeiras, and Azores), as well as Iceland, but otherwise its western 
and northern limits are those of Europe and Asia, with the more or 
less explored Arctic lands lying to the northward of them. 
Of the Provinces into which this vast area may be separated, 
there is first the ‘“ Siberian,” beginning on Bering’s Strait, and 
extending across the northernmost part of Asia to the confines of 
Europe, where what passes for the Ural Mountains may be found 
a convenient though probably an arbitrary boundary. Guided by 
the investigations of the late Capt. Blakiston and Mr. H. Pryer,! we 
find that the Strait of Tsugaru, between Yezo and Nipon (occa- 
sionally called Hondo), constitutes a boundary between two Pro- 
vinces, the more northern being that first named, while the more 
1 Trans. Asiat. Soc. Japan, x. pp. 84-186 (1882), and Amended List of the 
Birds of Japan (London: 1884). 
