AVES. 
77 
the Psittaci of the same region, noticed last year (Zool. Record, 
i. pp. 53-55). Like that group of birds, the ColumbcB attain 
their maximum development in the limited district of which the 
great island of New Guinea forms the centre, and which he 
calls the Austro-Malayan subregion. Its actual land-area is 
less than one-sixth of Europe, and yet it contains more than a 
fourth of all the species of Pigeons known to exist. This 
peculiar distribution is, Mr. Wallace suggests, owing to the 
total absence from it of all forest-haunting and fruit-eating 
mammals, such as Monkeys and Squirrels ; at least the converse 
is no doubt the reason why, in the Amazon valley. Pigeons are 
scarce or almost entirely absent, such species as there are having 
mostly habits of feeding on the ground and breeding lower in 
the bushes than Monkeys descend. In the Malay countries 
also there are no great families of fruit-eating Passeres, and 
their place seems to be taken by the true Fruit-Pigeons, which, 
unchecked by rivals or enemies, often form with the Psittaci 
the prominent and characteristic features of the avifauna. 
Mr. Wallace divides the order Columbce into three great 
families : the TreronidcCy with short legs and broad-soled grasp- 
ing feet, feeding entirely on fruit, and never descending to the 
ground, are entirely confined to the eastern hemisphere ; the 
true ColumbidcR, with larger feet but slenderer toes, feeding either 
on the trees or on the ground, are of the most general distribu- 
tion ; and the GouridcSy with longer legs, running quickly, feed- 
ing always on the ground, and only ascending trees to roost, 
chiefly abound in the Australian and [South] American regions. 
Each of these families is distinguished by a characteristic type 
of colouring. 
Of the Treronid(B fifty-four species are confined to the Austro- 
Malayan, while twenty-eight inhabit the Indo-Malayan sub- 
region. In India fourteen, and in Africa six species (all of the 
same genus Treron) are found ; thirty inhabit the Pacific islands ; 
and eight occur in Australia or New Zealand ; while New Guinea 
has fourteen species. 
The true Colmnbida are, in the Archipelago, chiefly repre- 
sented by the genus Macropygia, but more than a single 
species is rarely found in any one island, except Java. The 
Old-World genus Turtur has a few representative species in the 
Indo-Malay islands, but does not properly extend to the Austra- 
lian region. 
Of the seven genera of Gourid(S found in the Archipelago^ 
only two extend to the continent of Asia, while five are confined 
to the Austro-Malayan subregion, and three to New Guinea. 
The singular Calcenas nicobarica Mr. Wallace believes to have 
spread westward from New Guinea to the islands whence it 
takes its name. The other genera have a very limited range, 
Chalcophaps being the only exception ; but all its species are 
