igo;.] 



Dr. Hossack : The Rats of Calcutta. 



II 



Table contrasting the skull measurements of immature with those of adult rats. 







Percentage 



; of total length of skull. 





.a 



c 



Ö 



r 



c 

 



+-1 

 COD 



C 



Cranial breadth. 







13 



u 



(U 



-t-" 



Ö 



Length of zygo- 

 matic plate. 



cd 



a 



tn 







Length of upper 

 molar series. 



M. decumamis 



34 



33-8 



43-3 



16-9 



11 



26-4 



22 



Do. 



33 



34-6 



45-4 



16-6 



10-6 



27-2 



21-2 



Do. 



35 



32-8 



44-2 



171 11-4 



27-2 



21-4 



Do. , adult . . 



510 



38-7 



33-6 



141 13-7 



29-4 



14-9 



N. bengalensis 



29 



27-5 



50 



17-2 



13-7 



27-5 



24-1 



Do. 



285 



25-4 



491 



18-4 



1403 



28-07 



24-5 



Do. .. .... 



28 



28-5 



50 



17-8 



14-2 



27-67 



23-2 



Do., adult . . 



39-6 



29-4 



42-0 



15-81 



16-16 



3106 



18-05 



M. rattus 



28 



33-9 



50 



19-6 



8-9 



25 



25 



Do. 



31 



32-2 



48-3 



1 



17-7 



9-6 



25-8 



21-7 



Do. 



31 



32-5 



50 



161 



10-4 



25-8 



22-5 



Do., adult of 17 cm. length 



41-5 



35-7 



! 37-4 



13-9 



12-4 



27-5 



17-1 



N. bandicota 



44 



311 



40-9 



15-9 



13-6 



29-7 



22-7J 



Do. , adult . . 



63-6 



36-3 



34-8 



13-97 



171 



31-43 



18-69 



KEY TO THE RATS OF CAI.CUTTA. 



A. I^ONG-TAiLED, i.e., tail = 125 to 135 per cent, of length of head and body. 



1. Small to medium sized ; slender body ; ears long and wide and stand out 

 from head ; eyes very large and prominent ; feet slender, white but sometimes dark ; 

 median pads of hind foot cordiform, external pad generally with small extra tubercle ; 

 tail uniformly dark. House rat. — Mus rattus (alexandrinus) : the Black Rat. 



B. Short- or Medium-tailed, i.e., tallage per cent, of length of head and 

 body. 



2. Heavy-bodied rat, with large, heavy tail which is generally white or distinctly 

 light in lower half ; eyes small ; distinguished from N. bengalensis by feet which are 

 large, heavy and flesh-coloured with cordiform median pads like rattus ; jowl heavy 



