148 NATURAL HISTORY OF THE [chap. ix. 



bntioii of birds and iraniraalia, and rendering it almost 

 certain that tliu last-named island was tlie first to be com- 

 pletely separated from the Asiatic continent, and that the 

 native tradition of its ha\ang been recently separated from 

 Sumatra is entirely without foundation, 



AVe are now enabled to trace out with some probabiUty 

 the course of events. Beginning at the time when 

 the whole of the Java sea, the Gulf of Siam, and the 

 Siraita of Malacca were diy land, forming with Borneo, 

 Sumatra, and Java, a vast southern prolongation of the 

 Asiatic continent, the first movement would be the sink- 

 ing down of the Java sea, and the Straits of Sunda, con- 

 sequent on the activity of the Javanese volcanoes alon^j; 

 the sonthern extremity of the land, and leading to the 

 complete separation of that island. As the volcanic belt 

 of Java and Sumatra increased in activity, more and more 

 of the land was submerged, till first Borneo, and after- 

 wards Sumatra, became enthvly severed. Since the epoch of 

 the first disturbance, several distinct elevations and depres- 

 sions may have taken place, and the islands may have been 

 more than once jobed with each other or with the main 

 lanil, and again separated. Successive waves of immigra- 

 tion may thus have modified their animal productions, 

 and led to those anomalies in distribution which are so 

 difficult to account for by any single operation of elevation 

 or submergence. The form of Borneo, consisting of mdiat- 

 ing mountain chains with interv^enjjig broad aUuviid 

 valleys, suggests the idea that it has once been much more 

 submerged than it is at present (when it would have 

 somewhat resembled Celebes or Gilolo in outline), and has 

 been inci-eased to its present dimensions by the fiUing up 

 of its gulfs with sedimentary matter, assisted by gradual 

 elevation of the land. Sumatra has also been evidently 

 much increased in size by the formation of alluvial plains 

 along its north-eastern coasts. 



There is one peculiarity in the productions of Java that 

 is very puzzling — the occurrence of several species or 

 groups characteristic of the Siamese countries or of India, 

 but which do not occur in Borneo or Sumatra. Among 

 Mammals the Khinoceros javanicus is the most striking 

 example, for a distinct species is found in Borneo and 



