VIII.] RODENTIA. 277 



siderable elevations in Java, as well as in Sumatra and Borneo. 

 No fossil representatives of either of these two genera are at 

 present known. 



Among the rodents, the grooved-toothed squirrel (Rhithro- 

 scturus) is a peculiar type confined to the island of Borneo; 

 and the pigmy squirrels (Nannosciurus) are represented by four 

 Malayan species, the only other member of the genus being West 

 African. The true squirrels (Sciurus), as mentioned above, attain 

 their maximum development in the Malayan sub-region. The 

 flying - squirrels are represented by the genera Pteromys and 

 Sciuropterus, the former being exclusively Oriental, and the latter 

 having one species in the eastern, and a second in the western 

 half of the Holarctic region, in addition to being represented in a 

 fossil state in the French Miocene. In the Muridcz there are no 

 less than eleven genera in most cases respectively represented 

 by only a single species peculiar to this region, while another is 

 Oriental and Ethiopian only. Of the peculiar types, one of the 

 most remarkable is Chrotomys, from the mountains of Luzon, in 

 the Philippines, belonging to the sub-family Hydromyince, of which 

 the typical forms are Australian 1 . From other members of the 

 sub-family the single species of this genus differs in having three 

 (in place of only two) pairs of molar teeth, thereby forming a 

 link with ordinary murines. This animal, which is about the 

 size of a rat, is easily recognised by the presence of an orange or 

 buff line running down the middle of the back. Luzon has also 

 yielded another rat, provisionally referred to the Australian genus 

 Xeromys*. Another unique Oriental type is found in the long- 

 tailed dormouse-like form from the Malabar coast known as 

 Platacanthomys, which constitutes a sub-family by itself. Phlao- 

 mys, likewise representing a separate group of the same rank, is 

 restricted to the Philippines, and is characterised by the molar 

 teeth being divided into three transverse lobes. The one species 

 is of very large size. Nearly allied is a huge, rough-haired, grey 

 or blackish rat, from the mountains of Luzon, which may be 

 compared in size to a small marmot, and for which the name 

 Crateromys has been suggested. This differs from Phlceomys by 



1 Vide suprh, p. 40. 



2 Appendix, No. 31 



