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Show 358 ISLAND LIFE. [rAnT u. Malay countries being represented in Java by distinct but closely allied species. From these f::wts it is impossible to doubt that Java has had a history of its own, quite distinct from that of the other portions of the Malayan area. Special relations of the Javan Fauna to that of the A siat1:c Oontinent.-These relations are indicated by comparatively few examples, but they are very clear and of great importance. Among mammalia, the genus Helictis is found in Java but in no other Malay country, though it inhabits also North India ; while two species, Rhinoceros }avanic'us and Lepus ktwgosa, are natives of Indo-Chinese countries and Java, but not of typical Malaya. In birds there are three genera.-Zoothera, N otodela, and Crypsirhina, which inhabit Java and Indo-China ; while four others-Brachypteryx, Allotrius, Cochoa, and Psaltria, inhabit Java and the Himalayas, but no intervening country. There are also two species of birds-a trogon (Harpactes oreslcios), and the Javanese peacock (Pavo muticus), which inhabit only Java and the Indo-Chinese Peninsula. Here, then, we find a series of remarkable simHarities between Java and the Asiatic continent, quite independent of the typical. Malay countries-Borneo, Sumatra, and the :1\'Ialay Peninsula, which latter have evidently formed one connected land, and thus appear to preclude any independent union of Java and Siam. The great difficulty in explaining these facts is, that all the tequired changes of sea and land must have occurred within the period of existing species of mammalia. Sumatra, Borneo, and Malacca are, as we have seen, almost precisely alike as regards their species of mammals and birds; while Java, though it differs from them in so curious a manner ; has no greater degree of speciality, since its species, when not Malayan, are almost all Indian or Siamese. .Th~re is, however, one consideration which may help us over th1~ difficult~. It seems highly probable that in the equatorial regiOns species have changed less rapidly than in the north temperate ~one, .on account of the equality and stability of the equatonal chmate. We have seen, in Chapter X., how CHAP. XVI!.] BORNEO AND JAVA. 359 important an agent in producing extinction and modification of species must have been the repeated changes from cold to warm, and from warm to cold conditions, with the inevitable migrations and crowding together that must have been their necessary consequence. But in the lowlands, near the equator, these changes would be very little felt, and thus one great cause of specific modification would be wanting. Let us now see whether we can sketch out a series of not improbable changes which may have brougl1t about the existing relations of Java and Borneo to the continent. Past Geographical Changes of Java ancl Borneo.-Although Java and Sumatra are mainly volcanic, they are by no means whoHy so. Sumatra possesses in its great mountain masses ancient crystalline rocks with much granite, while there are extensive Tertiary deposits of Eocene age, overlying which are numerous beds of coal now raised up many thousand feet above the sea.1 The volcanoes appear to have burst through these older mountains, and to have partly covered them as well as great areas of the lowlands with the product of their eruptions. In Java either the fundamental strata were less extensive and less raised above the sea, or the period of volcanic action has been of longer duration; for here no crystalline rocks have been found except a few bouluers of granite in the western part of the island, perhaps a relic of a formation destroyed by denudation, or covered up by volcanic deposits. In the southern part of Java, however, there is an extensive range of low mountains, about 3, 000 feet high, consisting of basalt with limestone apparently of Miocene age. During this last-named period, then, Java '\vould have been at least 3,000 feet lower than it is now, and such a depression would probably extend to considerable parts of Sumatra and Borneo, so as to reduce them all to a few small islands. At some later period a gradual elevation occurred, which ultimately united the whole of the islands with the continent. This may have continued till the glacial period of the northern hemisphere, during the severest part of '"hich a few Himalayan 1 ''On the Geology of Sumatra," by M. R. D. M. Verbeck. Geological ]If agazine, 1877. |
