CHAP. XIX.] 
THE MADAGASCAR GROUP. 
407 
The smaller and more remote Rodriguez is also volcanic; but it 
has, besides, a good deal of coralline rock, an indication of partial 
submergence and helping to account for the poverty of its faunas 
and flora. It stands on a 100-fathom bank of considerable extent, 
but beyond this the sea rapidly deepens to more than 2,000 
fathoms, so that it is truly oceanic like its larger sister isles. 
Birds . — The living birds of these islands are few in number 
and consist mainly of peculiar species of Mascarene types, 
together with two peculiar genera — Oxynotus belonging to the 
Campephagidse or caterpillar- catchers, a family abundant in the 
old-world tropics ; and a dove, Trocazza, forming a peculiar sub- 
genus. The origin of these birds offers no difficulty, looking at 
the position of the islands and of the surrounding shoals and 
islets. 
Extinct Birds . — These three islands are, however, pre-eminently 
remarkable as being the home of a group of large ground-birds, 
quite incapable of flight, and altogether unlike anything found 
elsewhere on the globe ; and which, though once very abundant, 
have become totally extinct within the last two hundred years. 
The best known of these birds is the dodo, which inhabited 
Mauritius ; while allied species certainly lived in Bourbon and 
Rodriguez, abundant remains of the species of the latter island 
— the “solitaire,” having been discovered, corresponding with the 
figure and description given of it by Legouat, who resided in 
Rodriguez in 1692. These birds constitute a distinct family, 
Dididae, allied to the pigeons but very isolated. They were 
quite helpless, and were rapidly exterminated when man intro- 
duced dogs, pigs, and cats into the islands, and himself sought 
them for food. The fact that such perfectly defenceless creatures 
survived in great abundance to a quite recent period in these 
three islands only, while there is no evidence of their ever 
having inhabited any other countries whatever, is itself almost 
demonstrative that Mauritius, Bourbon, and Rodriguez are very 
ancient but truly oceanic islands. From what we know of the 
general similarity of Miocene birds to living genera and families, 
it seems clear that the origin of so remarkable a type as the 
dodos must date back to early Tertiary times. If we suppose 
some ancestral ground-feeding pigeon of large size to have 
c 
