22 Records of iJie Indian Museum. [Vol. Ill, 



irregularity' of the diagram is clue to the large number of young ones 

 included. The adult maximum is indicated at i8o — 185 mm., which 

 seems somewhat high. 



The tail proportion was calculated in twenty- adults ; after 

 making the ±10 mm. correction it is found to vary from 127 % 

 to 102 % with average of 115 "3 %. This is low for the Punjab ; 

 much lower than the proportion shown by the Calcutta race. The 

 skulls of these white-bellied rats were not found to differ from those 

 of the common Punjab race, which do not seem to differ from the 

 mixed Calcutta race in this respect. These rats are not all of the 

 pure white-bellied type ; man}- of them have a coloured stripe in 

 the middle of the breast ; they resemble the Simla race (Sml. 2) in 

 this and all other respects. 



Pjb. 3, " Mus brahminicus " — 



Among the house rats sent by Davj's were two of exceptional 

 interest. These resemble one another almost exactly but differ 

 from the common race in more than one respect. They both have a 

 well-marked white star on the forehead, and the terminal third of 

 the tail is pure white. These features are shown in plate i. The 

 sender alluded to them tentatively as a new species ' ' Mus brah- 

 minicus ' ' (so called from the ' ' caste mark ' ' on the forehead) ; and 

 there is no doubt that their peculiarities are better marked than 

 those of many species of the Mus r alius group. Since at least 

 twenty-two thousand house rats not showing these peculiarities 

 were captured in the district from which these two were obtained, 

 one cannot regard the pair as part of an established race. 



The writer supposes them to be part of a " family group ' ' of 

 sports exactl}^ comparable to the groups Rng. 8 and Ntl. 2. Such 

 groups are too limited in their membership at present to be dignified 

 by the term ' ' race ' ' ; however they must each have some slender 

 chance, varying directly with their fitness, of becoming a race. 



The measurements of these rats, recorded by the sender, are 

 as follows : — 



163 172 31 14 85 grms. 



163 167 29 13 95 grms. 



they are both of a much lighter colour than the average Punjab 

 rat, their under parts are white, both were certainly- adult, the 

 female was pregnant (four embryos). Besides resembling one another 

 closely and differing widely from the average rat in colour, they 

 resemble one another closel}' in length and weight and differ from 

 the mean length (180 mm.) and mean weight (140 grms.) of the 

 Punjab race. 



This pair of sports is biologically of the utmost interest. The 

 most noticeable peculiarity which they exihibit is the absence of 

 pigment from the terminal third of the tail. The change from the 

 pigmented portioij to the unpigmented is very sudden, so that 

 one scale possesses its full complement and the next is totally de- 

 void of pigment. The change was so sudden that it called to mind 



