VIII.] SUB-REGIONS. 303 



Although not taking into account the relationship between the 

 fauna of Borneo and that of the Palawan sub-group, this may 

 be accepted as, on the whole, a very probable explanation of 

 the facts of the case. It may be added that while the Javan 

 rhinoceros (. sondaicus] is, as already stated, closely allied to the 

 Siwalik R. sivalensis, the nearest ally of R. sumatrensis appears to 

 be the extinct R. schleiermacheri of the European Miocene, thus 

 affording one more instance of affinity between the typical Ma- 

 layan fauna and that of the middle Tertiaries of Europe. 



Recent investigations on the mammals from some of the small 

 chain of islands lying to the south-west of Sumatra, 

 such as Nias and Sipora in the Mentawi group, to- 

 gether with Christmas Island 1 , lying still further to Christmas 



Islands. 



the south, have shown that they differ very markedly 

 from those of the larger islands. From Sipora, in addition to 

 bats, Mr O. Thomas 2 records the following species, of which those 

 peculiar to the island are printed in italics : 



Semnopithecus potenziani. 



Macacus nemestrinus. Widely spread. 



Tupaia ferruginea, var. hypochrysa. Java. 



Paradoxurus, sp. 



Pteromys nitidus. Widely distributed. 



Sciuropterus lugens. 



,, aurantiacus. Banka. 



Sciurus melanogaster. 

 ,, fraterculus. 



Mus siporanus. 



raja. N. Borneo. 



From Christmas Island the same writer 3 records a peculiar 

 species of fruit-bat (Pteropus natalis], a variety of a widely-spread 

 musk-shrew (Croddura fuliginosa), and two peculiar rats (Mus 

 macleari, and M. nativitatis], remarkable for their large size. 

 Regarding the bearings of the faunas of these islands on the 

 general problem of distribution, Mr Thomas writes that the collec- 



1 This must not be confounded with the island of the same name in 

 Polynesia. 



2 Ann. Mus. Civ. Genova, Ser. 2, vol. xiv. pp. 660 672 (1895). 



3 Proc. Zool. Soc. 1887, pp. 511514, and 1888, pp. 532 534. 



