The Malay archipelago : the land of the orang-utan ... - Wallace Online

XIV.] NATURAL HISTORY OF TBIOR. 159west coast of Australia, and at one place approaching withintwenty miles of the coast of Timor. This indicates a recentsubsidence of North Australia, which probably once extendedas far as the edge of this bank, between which and Timor thereis an unfatliomed depth of ocean.I do not think that Timor was ever actually connected withAustralia, because such a large number of very abundant andcharacteristic groups of Australian birds are quite absent, andnot a single Australian mammal has entered Timor ; whichwould certainly not have been the case had the lands beenactually united. Such groups as the bower birds (Ptilonorhynchus),the black and red cockatoos (Calyptoi-hynchus), theblue wrens (Malurus), the crowslirikes (Cracticus), the Australianshrikes (Falcunculus andColluricincla), and many others, whichabound all over Australia, would certainly have spread intoTimor if it had been united to that country, or even if for anylong time it had approached nearer to it than twenty miles.Neither do any of the most characteristic groups of Australianinsects occur in Timor ; so that everything combines to indicatethat a strait of tlie sea has always separated it from Australia,but that at one period this strait was reduced to a width ofabout twenty miles.But at the time when this narrowing of the sea took place inone direction, there must have been a greater separation at theother end of the chain, or we should find more equality in thenumbers of identical and representative species derived fromeach extremity. It is true that the widening of the strait at theAustralian end by subsidence, would, by putting a stop to immigrationand inter-crossing of individuals from the mothercountry, have allowed full scojDe to the causes which have led tothe modification of the species ; while the continued stream ofimmigrants from Java, w'ould by continual intercrossing, checksuch modification. This view will not, however, explain all thefacts ; for the character of the fauna of the Timorese group isindicated as well by the forms which are absent from it as bythose which it contains, and is by this kind of evidence shownto be much more Australian than Indian. No less than twentyninegeiiera, all more or less abundant in Java, and most ofwhich range over a Avide area, are altogether absent ; while ofthe equally diff'used Australian genera only about fourteen arewanting. This would clearly indicate that there has been, tillrecently, a w'ide separation from Java ; and the fact that theislands of Bali and Lombock are small, and are almost whollyvolcanic, and contain a smaller number of modified forms thanthe other islands, would point them out as of comparativelyrecent origin. A wide arm of the sea jDrobably occupied theirplace at the time when Timor was in the closest proximity toAustralia ; and as the subterranean fires were slowly piling upthe now fertile islands of Bali and Lombock, the northern shoresof Australia would be sinking beneath the ocean. Some such