GEOGRAPHICAL DISTRIBUTION 333 
Perhaps there is nothing very surprising in this, when we con- 
sider the narrowness of the channel which here divides America 
from Asia, and furthermore the fact that the water of Bering’s 
Strait is shallow suggests a still closer connexion in bygone times 
of the two continents. The Aleutian Islands, though they look 
like a series of stepping-stones from one to the other, do not seem 
to furnish a route of communication, for Mr. Dall (Proc. Californ. 
Acad. Sc. 14 March 1874) calls special attention to the fact that 
no intrusion of Asiatic forms occurs towards the western end of the 
chain, while observing that its Avifauna is reinforced beyond 
Ounalaska by several Arctic species not.possessed by the more 
eastern islands. The other islands belonging to the Nearctie Sub- 
region, the Prybilof in the Northern Pacific, and the Bermudas 
nearly in the middle of the Northern Atlantic Ocean, do not need 
any particular remark here. Greenland may be regarded as coming 
almost into the same category, and though there, as might be 
expected, the influence of the Old World is strong, that of the New 
World just prevails, since of the 45 genera to which belong the 
feathered denizens of the fringe of habitable soil on its western 
coast (which is all that is offered by that land of desolation) 
none is especially characteristic of the former, while one, Zonotrichia, 
is peculiar to the latter, and a similar result follows from an investi- 
gation of the species—a bare majority being Nearctic.1 
It has been already stated that more than one-third of the 
genera of Nearctic birds are common also to the Palearctic Sub- 
region. If we take the number of Nearctic species at 700, which 
is perhaps an exaggeration, and that of Palearctic at 850, we find 
that, exclusive of stragglers, there are about 120 common to the 
two areas. Nearly 20 more are properly Palearctic, but occa- 
sionally occur in America, and about 50 are Nearctic, which from 
time to time stray to Europe or Asia.” This, however, is by no 
means the only point of resemblance. Of many genera, the so- 
- ealled species found in the New World are represented in the Old 
by forms so like them that often none but an expert can distinguish 
them, and of such representative “species” about 80 might be 
enumerated. 
this the writer fully believes them to be, more than one-half the Avifauna of 
these portions of the two continents would be the same. 
1 Any one at all curious in these questions should consult Prof. Palmén’s 
tables at the end of his contribution to the ornithology of the Siberian coast, 
printed in the fifth volume of the Scientific Results of the Voyage of the ‘ Vega.’ 
2 Baird, in the essay before cited, has reasonably accounted for this dispro- 
portionate reciprocity between Europe and America ; but perhaps more than he 
has allowed for must be set down to the comparative want until lately of records 
in the newer country. This want is being speedily supplied by the increased 
study of Ornithology of recent years in Canada and the United States. 
