igo;.] 



Dr. Hossack: The Rats of Calcutta. 



Table contras'.ing the body measurements of immaturity and adult life. 





Total length 

 of body in \ 

 centimetres. 



Percentage of body length. 



A 





Tail. 



Hind 

 foot. 



Ear. 



N. bengalensis 



10*2 



81-37 



22-54 



15-68 



Do. 



93 



80-46 24-73 



16-12 



Do. 



9 



77-77 25-55 



15-55 



Do., adult 



i8i6 



81 



17 



10-7 



M. dccnmanns 



II-5 



95-6 



28-7 



15-6 



Do. .. .. .. 



II-3 



97 



28 



15-8 



Do. 



ii'5 



85 



30 



16-5 



Do. , adult 



226 



89 



18 



8-2 



M. raUus . . 



10 



145 



29 



19 



Do. .. 



95 



147-3 



31-5 



18-9 



Do. .. 



10-5 



128-5 



27-6 



161 



Do , adult 



17-3 



121 ' 19-1 



12-1 



N. handicota 



17-5 



88-5 



26 



14-5 



Do., adult 



269 



94-5 



19-18 



10-2 



M. btanfordi 



10-25 



148 



29-2 



17 



Do., adult 



15 



130 



22-1 \ 



As regards cranial measurements it will be seen that the table bears out the general 

 statement already made, that in early youth the proportional cranial measurements 

 tend to be larger, while the facial measurements tend to be smaller. This is shown 

 particularly in the measurements of the nasals, the cranial breadth, both maximum 

 and interorbital, and the length of the zygomatic plate and the diastema, while the 

 most marked characteristic of all is the enormously increased relative dimension of 

 the molar series. This is due to the fact that the molars, even before they have cut 

 the gum, are already practically full grown, as far as length and breadth go, having to 

 increase in depth only. The third upper molar, the only one I have observed uncut, 

 occupies practically the same area as a full-grown tooth at a stage at which it is still 

 merely a plate of dentine showing no more than an indication of tubercular ridges 

 and only the rudiments of the large posterior fang. From the two measurements 

 that show the greatest divergence, the following law may be laid down ;— 

 2 



