70 



Records of the Indian Museum. 



[Vol. Ill, 



importation of the common Mus rattus type. There is one inter- 

 esting white-bellied rat measuring 147, 153, 30, 18 which has teats 

 of the Mus concolor formula (f). 



Measurements of five chance-taken skulls of adult Mus concolor. 



These skulls show no difference in their proportions from the 

 Mus rattus type. 



These three divisions A, B and C of Rng. i might be more 

 finely subdivided. A large number of mixed concolor taken from 

 all parts of the city could be arranged so as to show " interme- 

 diates ' ' not only between the subdivisions but between the divi- 

 sions. In spite of this, divisions and subdivisions are definite 

 entities, for rats found together in one house are nearly always of 

 the same type. Melanotic or semi-melanotic concolors are compara- 

 tively rare, but they are caught, not singly, but three or four at a 

 time. 



Rng. 2— 



A race of the Mus rattus type, the members of which are of 

 medium size, have white under parts and comparatively short tails 

 of uniform dtrk colour ; the females have teats almost invariably |. 



The peculiarities of this race are illustrated in the diagram 

 (plate v). The mean length of the race is about 145 mm. The tail 

 length averages about 105 per cent, of the length. The zigzag line 

 Ct. shows that the percentage is lower in this race than in concolor. 

 The teats were counted in eight mature females ; in six of them 

 they were -^, in one |, in another |, As regards colour tliey all 

 agree in possessing white under parts sharply defined from the 

 brown upper parts. In most of them the white is pure, but grey 

 median breast stripes of varying width and length are not uncom- 

 mon. In a few specimens all the ventral hairs have light grey 

 bases and white tips. As regards colour of the upper parts, perhaps 

 the commonest type is a dull greyish brown almost exactly like a 



