40 Records of the Indian Museum. [Vol. Ill, 



differ from lowland rats in this respect, l)ut in most of them the 

 fur is plentiful, long and soft, and devoid of spines and bristles. 

 Those with long soft hair usually have white-fringed ears. No type 

 of fur is peculiar to any one local group. The individual with the 

 longest and softest fur belongs to the Ayapata group, but the same 

 group contains a specimen with somewhat bristly scanty fur. An 

 old rat from the Brewery is conspicuous for the length and softness 

 of its fur, which is devoid of bristles. 



It must be strongly emphasized that the average quality and 

 colour of the fur in the Ayapata group is not different from that 

 of the rats found at the level of the lake. All are variable, but 

 specimens can be readily selected from the Ayapata group and 

 from the lake group which exactly resemble one another, except 

 in the coloration of the tail. The truth of this cannot be too strongly 

 expressed. 



Ntl. 2, the Ayapata group — 



The circumstances of the Ayapata group will be related in 

 some detail as they are of great biological interest. Traps were 

 set in a certain house on Ayapata Hill. The first capture was of two 

 young rats caught together on the same night and in the same 

 cupboard. These were so equal in their immaturity, that they 

 were considered to be of the same litter. At first sight they did 

 not seem to differ from the young rats of the bazaar. They were 

 coated with soft dark grey fur, and their tails were relatively short. 

 The tail of one of them was perfectly bicoloured, the lower half of 

 its circumference was devoid of pigment and bore white hairs, the 

 upper half was deeply pigmented and bore black hairs. The line 

 of demarcation was sudden. The second specimen resembled the 

 first except that the pigmented area of the upper surface did not 

 reach to the tip of the tail, so that rather more than a third of the 

 terminal portion of the tail was white in its whole circumference. 



These two specimens caused great perplexity. By every 

 systematic rule they should be of different species, each, again, 

 being different from that found in the bazaar. The specimen with 

 the completely bicoloured tail should be either Mus vicercx or Mus 

 niveiventer , both of which species occur in the Himalayas and have 

 short bicoloured tails; it is especially like the latter, which has greyish 

 fur. The other specimen, in its partially bicoloured tail, resembles 

 Mus berdmorei [4], a species which has been found in Manipur and 

 Tenasserim, but not in the countries between. The circumstances, 

 however, plainly indicate that these two rats are of the same race 

 and that they are more nearly related to the rats of Naini Bazaar 

 than to Mus niveiventer , which was discovered fifty rat-generations 

 ago in Katmandu but has not been rediscovered. 



Traps were set in a neighbouring house and in the interven- 

 ing outhouses, with the result that six more rats were caught ; 

 the tails of all of them were pure white below, the pigmentation 

 of the upper surface extending along the tail to a variable distance 



