igoy.] Dr. Hossack : The Rats of Calcutta. 27 



M anus. —Covered with short, Hght brown or dirty white hairs. Pollex tubercular 

 with nail. The other digits show strong, horny white claws, by no means always worn 

 and blunted as sometimes described. The palm, which is flesh coloured, shows five 

 pads. 



Pes. — Flesh-coloured, thinly covered with short, white hairs, which, on the outer 

 margin of the foot, are sometimes brownish. All the digits are armed with stout, horny 

 white claws, surmoiuited by a little tuft of longer white hairs. The sole of the foot 

 is flesh coloured and shows six prominent fleshy pads. The median ones are cordiform, 

 and that at the base of the fifth digit frequently shows an attached tubercular pad, 

 which in Mus rattus is nearly constant. The proximo-external pad is large and fleshy, 

 unlike the small rudimentary one found in Nesokia hengalensis. Next to the tail the 

 pads form the most reliable distinction between these two rats as far as external charac- 

 ters go, though the relative proportions of the length of the foot are very distinctive 

 also. 



Ears. — Short and rounded, nearly naked, and of a brownish flesh colour ; covered 

 with very minute hairs , lower part of the posterior surface nearly naked. When 

 laid forward in 42 per cent, of individuals they came short of the eye, the interval 

 varying from '2 cm. to i cm. In 26 per cent, the ear reached the eye. In 14 per 

 cent, it half covered the eye ; in 4 per cent it covered the eye, and in 14 per cent, the 

 relation of ear to eye was not noted. It will be noted how very unsatisfactory is this 

 point as a diagnostic test, particularly as it is very difficult to apply it in a constant 

 manner. 



Mammce. — These characteristically number three pairs pectoral and three pairs 

 inguinal but are rather variable as this distribution was found in only 11 out of 19 

 specimens. 



In four instances f was the formula, in one case ^, in one case f , and twice they 

 were found unsymmetrical f f and f f . 



Habits. — This rat is essentially parasitic in its habits, frequenting sewers, drains, 

 cellars and generally the basements of houses, and burrowing there. Even where the 

 upper stories are composed solely of masonry and iron, as is generally found in 

 houses of modern construction in Calcutta, these rats are frequently trapped upstairs 

 at night, gaining access by waste- water pipes and the like. I have watched them come 

 out from a drain in a courtyard, enter the outlet of an iron pipe, and presently appear 

 in an upper verandah where they skirmished about for food. With my companion I 

 watched them, for a considerable time playing about between the drain and the upper 

 verandah. When caged their demeanour is quite different from Nesokia hengalensis ; 

 they take things quite quietly and philosophically and never dash wildly about. They 

 never erect their fur and gnash their teeth. The figures given in my preliminary pote 

 as to the relative frequency of M. decumanus, were collected in Districts I and II where 

 grain godowns abound, and Nesokia is in consequence the predominant rat. In 

 District III, which collects rats caught in and about the Municipal Market and the 

 surrounding quarters, M. decumanus accounts for half of the rats sent in. 



