66 MR. C. BODEN KLOSS ON 



orbus,- a member of the bicoloured-tailed section (The curve of the 

 incisors is not a very satisfactory character in this connection, as the 

 differences are not great, but the skulls of s^me of the rats of the 

 group are so alike that it is of some use). R. blythi is also a larger 

 animal and in size comes near jR. c. tenaster. 3 



R. blythi differs from orbus in having much less intensely 

 coloured upper parts and whiter undersurface : has a shorter tail 

 with a larger white area, narrower interpterygoid space, narrower, 

 more parallel-sided, palatal foramina. 



The skull and teeth of blythi do not appear to differ mate- 

 rially from those of Rnttus bukit, * bub the fur is brighter coloured 

 above and whiter below ; the white of the hind leg is more' fre- 

 quently cut off from that of the foot ; the hair of the tail distally 

 is often white above, while that of bukit is dark ; and the pelage is 

 looser, less compact of spines and not so stiff (thus like crcmori- 

 venter). 



In the same way that the upper incisors of blythi and bukit 

 differ from cremoriventer, so do those of marinus. •"' However, blythi 

 may be distinguished from this last by its smaller palatal foramina 

 and narrower interpterygoid space, while its colour is a little 

 brighter above and less creamy below. 



The differences between the above forms may be set out as 

 follows : — 



A. Tail unicoloured, somewhat pencillate, incisors 

 less curved backwards. 



a. Smaller. ... ... . .. It. c. cremori venter. 



b. Larger. ... ... ... R. c. tenaster. 



B. Tail bicoloured, no longish hairs at tip. 



a. Incisors le-s carved backwards, tail with 



less white below and generally over 



200 mm. long, bullae larger. ... Ii. orbus, 



b. Incisors more curved backwards, tail with 



more white below and generally less than 

 200 mm. long, bullae smaller 

 «1 Palatal foramina larger. ... ii?. marinus. 



bl Palatal foramina smaller. 



a'2 Colour duller, pelage stiffer. ... E. bukit. 

 b'2 Colour brighter, pelage less stiff* 7?. blythi. 



2, 3, 4, 5. Vide Notes on page 68 postea. 



JOURN. NAT. HIST. SOC. S1AM. 



