34G 



GEOaEAPHICAL DISTEIBUTiON OF SrECIES. [Ch. XXXVJII 



seems 



Indian region. — We have next to consider the Indian reo-ion 

 comprising' Southern Asia and the western half of the Malay 

 archipelago. Its boundary on the side of Arabia has not yet 



at present to be 

 regarded by zoologists as debateable ground between tLe 

 Ethiopian, Indian, and Palsearctic regions. Although the 

 Indian species are very distinct from those of Africa, a great 

 many of the genera of quadrupeds are common to both con- 

 tinents. There are, however, some forms which are peculiar 

 to the Indian region ; such as the sloth-bear {Prochihis)^ the 

 musk-deer {3Ioscus)^ the nylghau, the gibbon or lono^-armed 

 ape, and some others. 



The elephant and tapir of Sumatra and Borneo are the 

 same as the Indian species, and the rhinoceros of Sumatra and 

 that of Java are each of them respectively common to Bengal 



and Malacc 



One of the 



gibbons 



or 



long-armed 



apes 



common 



islands of Java and Borneo, though wanting in Sumatra. 

 The wild ox of Java also occurs on the Asiatic continent. 

 None of these large animals, says Mr. Wallace, could possibly 

 have passed over the arms of the sea which now separate 

 these countries ; so that they point clearly to the existence of 

 a land communication between the islands and the mainland 

 since the origin of sucli mammalia. 



Between 80 and 90 mammals inhabit Java^ and nearly as 

 many occur in Sumatra ; more than half of these species are 

 common to the two islands. Borneo, which is much less ex- 

 l)lored, has yielded already upwards of 60 species, and more 

 than half of these are not met with either in Java or Sumatra. 

 As each island contains not only many species but some genera 

 peculiar to itself, the date of their former union can only be 

 spoken of as modern when we understand the term in a geo- 

 logical sense. We may feel sure, for example, that it occurred 

 during some part of the Pliocene epoch ; and this speculation 

 is rendered the more probable by the fact that a difference of 

 level of 50 fathoms, or only 300 feet, w-ould unite Borneo, 

 Java, and Sumatra with the mainland or with Malacca and 

 Siam,-^- and a rise of 100 fathoms would include the Philippine 



* Wallace, Physical Goograph}- of Malay Archipelago, Geogr. Soc. Joiirn. 1864. 



