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inhabited by a considerable number of Mammals which, however, in all probability, also occur on the adjacent mainland.
The other islands above mentioned, Prince's Island, St. Thomas, and Anno Bon, are all considerably more distant from the coast of Africa, and, so far as we know, do not possess any native Mammals. A certain number of Landbirds have been obtained from these islands, and a few of these are peculiar, but they are all closely allied to forms that occur in the neighbouring West African mainland.
The most important islands in the Indian Ocean are, apart from Madagascar, Socotra, the Seychelles, the Amirante Islands, the Comoros, and finally Réunion, Mauritius, and Rodriguez.
Socotra is situated about 150 miles due east of Cape Guardafui, the extreme eastern point of Africa. Its fauna and flora were carefully investigated some years ago by Professor Bayley Balfour (1). He found that the only Mammals inhabiting the island are a Bat, which he was unable to obtain, and a Civet (Viverricula), met with also in South Asia, and probably introduced by human agency.
The Seychelles are distant about 700 miles from the northern point of Madagascar in a north-easterly direction, a more or less continuous chain of islands (Amirante, Providence, and Farquhar) forming a series of stepping-stones between them. But two narrow deep channels of over 1000 fathoms run between the Seychelles and Amirante on the one hand, and between Amirante and Providence on the other, thus cutting the Seychelles off from Madagascar by their deep water.
There do not appear to be any indigenous terrestrial Mammals in the Seychelles, except two Bats, which have been recorded as occurring there. The Land-birds are most of them peculiar, though belonging to genera found in Madagascar or Africa; the reptiles and amphibians are fairly numerous for islands such as these, and several of the species are not found elsewhere. It is difficult to say whether these islands have ever had a land-connection with Madagascar, but probably, if such were ever the case, it was at a remote time, geologically speaking.
The Comoros are a group of several islands lying about midway between the most northerly point of Madagascar and the mainland of Africa. They are separated from Africa by the Mozambique channel, more than 1000 fathoms in depth, while the depression between them and Madagascar is considerably less. Inhabiting these islands there are three Bats. Two of these are of the genus Pteropus, which is entirely absent from the mainland of Africa, but is found in Madagascar and many islands of the Indian Ocean. There is also a peculiar species of Lemur (Lemur mayottensis) and the Indian Civet (Viverricula), which last is also found in Madagascar and Socotra, and has in all probability been introduced by human agency. A fair proportion of the Land-birds of the Comoros, though in some instances peculiar, belong to Madagascar forms, and everything goes to show that the relation of this group of islands is with Madagascar rather than with the mainland.
The islands of Réunion, Mauritius, and Rodriguez are distant from Madagascar in an easterly direction 450, 550, and 800 miles respectively. They are all of volcanic origin, and separated from Madagascar by water of more than 2000 fathoms in depth. As would be expected, these islands are thoroughly Oceanic, and possess no indigenous Mammals or Amphibians; while the Land-birds are few in number, and belong mostly to genera found in Madagascar. The most remarkable feature, however, of the Fauna of these islands is the former existence of a group of flightless Ground-birds now quite extinct, but some of which were found in great numbers when the islands were first discovered. These are the Dodos of Mauritius and Réunion respectively, and the Solitaire of Rodriguez. These birds form a distinct family—the Dididæ, probably allied to the Pigeons, but of somewhat obscure affinities. It seems that the ancestors of these birds must have reached the islands in very early times, and that most of the striking peculiarities exhibited by them were gradually acquired after their arrival in the group.
We may, at any rate, conclude that these three islands are truly Oceanic, and that they have never had a landconnection with Madagascar or elsewhere.
SECTION II.-GENERAL VIEW OF THE MAMMAL-FAUNA
OF THE ETHIOPIAN REGION
The Ethiopian Region, as will be seen by looking at the Tables of the numbers of families, genera, and species given at the end of Chapter I. (p. 16), is the richest of the six Regions as regards the total numbers of its families, genera, and species of mammals, although the percentage of peculiar forms not found in other Regions is hardly so high as in the Neotropical and Australian Regions. This may, however, be accounted for by the consideration that there is a long land-frontier between the Ethiopian and the Palæarctic Regions, though this is chiefly occupied by desert.
Out of the nine orders of Terrestrial Mammals the Ethiopian Region contains representatives of seven, the
Marsupials and Monotremes being alone absent. The Edentates of this Region are represented by two families. One of these, of which the sole genus is the Aard-vark (Orycteropus), is quite restricted to the Region (see Fig. 13). The other, containing the scaly ant-eaters (Manidæ) is found also in the Oriental Region (see Fig. 14). These two forms are in most respects more closely allied to one another than to any of the Edentates of the New World.