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The endemic genera of Celebes are four in number, and judging from their affinities, it is impossible to believe that they have any relation to the animals now living in the Australian Region. Everything points to their being remains of a very ancient fauna, which must have been originally derived from the Asiatic continent.
The presence of the three Australian genera in Celebes does not in any way require the supposition of an ancient land-connection with that Region. This is obviously so in the case of the Bats, and the Phalanger is a strictly arboreal animal, and might easily have been drifted across a narrow strait on floating timber. On the other hand, to account for the greater proportion of Oriental forms found in the island, we are driven to the conclusion that at some time or other there has been some sort of land-connection between Celebes and the mainland of Asia. These are the principal reasons for transferring the island of Celebes from the Australian to the Oriental Region."
SECTION VIII.- THE PAST HISTORY OF THE ORIENTAL
MAMMAL-FAUNA Considerable controversy has arisen from time to time with regard to the similarities that undoubtedly exist between the faunas of the Oriental and Ethiopian Regions. Some writers have urged that, in order to account for this, some form of direct land-connection must have existed at one time or another across the Indian Ocean between Southern India and South Africa. Others have maintained that the points of similarity between the two faunas have been exaggerated, and that no such land-connection is required to account for the facts, which can easily be explained on the supposition of a southward emigration of northern forms due to glacial cold.
1 For the most recent information on the mammals of Celebes see Meye “Säugethiere von Celebes und Philippinen-Archipelago,” Abh. Mus. Dresden, vi., No. 6.
If we go back to the early part of the secondary epoch of geological time, we find, very well developed in India, a geological system known as the Gondwana, composed of sandstones and shales, which appear to be of fluviatile origin. These beds have long afforded a problem to geologists, as they cannot be at all satisfactorily correlated with any formations in Europe. In South Africa, however, we find a series of beds, also doubtless of fresh-water origin, known as the Karroo formation, which contains a nearly similar set of fossil remains, and in New South Wales, again, there are formations also agreeing in the characters of their fossils with the Gondwana beds. These facts, according to Mr. Oldham (3), our latest authority on this subject, are “ inexplicable, unless there has been a continuous land-communication along which plants could freely migrate, and the conclusion is vastly strengthened when we remember that throughout the great part, if not the whole, of this period, a very different type of flora was flourishing in Europe and North America."
This land-connection may be of use in explaining the distribution of some of the lower vertebrates, but is of no assistance so far as the Mammals are concerned ; because in those early times it is probable that none of the families or even orders of our present Mammals had arisen. The best-known and richest of the mammal-bearing formations of India are certain beds in Sind, and the Siwalik deposits lying along the foot of the Himalayas. These beds, especially the latter, contain the remains of an extensive and exceedingly interesting Mammalian fauna, which has hitherto been very inadequately explored, and will probably afford abundant opportunities of discovery to the paleontologist of the future.
The number of genera hitherto discovered in these formations amounts in all to about sixty, of which thirtynine are still in existence, while twenty-five are extinct. Among the recent genera are a considerable number which, though still occurring in Africa, have become extinct in the Oriental Region; such are Bubalis, Cobus, Oreas, and Strepsiceros—all genera of antelopes, Giraffa (the Giraffe), Hippopotamus, Loxodon (the African Elephant), Cynocephalus (the African Baboon), and Anthropopithecus (the Chimpanzee), while others still survive in India.
The most remarkable feature, however, of the Siwalik fauna is the fact that, while certain of the genera are only found in Miocene beds in Europe, and not in more recent deposits, the greater number are only known, out of India, from the Pliocene and Pleistocene, so that it is very difficult to fix the age of the Siwaliks as compared with the formations of Europe.
Beds containing a somewhat similar fauna, in most cases not so rich, have been discovered in Greece, near Athens, in Samos, and in one or two other localities, at least, in South-Western Europe; while north of the Alps nothing of the sort has been found of a corresponding age.
The most plausible explanation of the whole matter, therefore, so far as we can say at present, is that the increasing cold at the end of the Miocene and the beginning of the Pliocene times gradually drove the northern inhabitants southwards. It thus came to pass that, at that period of the world's history, the Mammalian faunas of Southern Europe, South-Eastern Asia, and of India were so nearly uniform as to constitute these countries, as regards their mammals, one widely extended Region.
LIST OF THE PRINCIPAL AUTHORITIES REFERRED TO IN CHAPTER V.
(1) MILNE-EDWARDS, H. ET A.—“Recherches pour servir à l'histoire naturelle des Mammifères.” Paris, 1868.
(2) BLANFORD, W. T.—“The Fauna of British India : Mammalia." London, 1888–91.
(3) OLDHAM, R. D.—“Manual of the Geology of India.” Calcutta, 1893.