THE BROWN OR COMMON RAT 613 



from silver to a light yellowish-brown. Except under the chin, where 

 the hairs are white throughout, all the hairs have slaty or dusky bases. 

 The ears are of a dull hair-brown. The hands and feet are greyish 

 flesh-coloured (not pink as in rattus). The tail is inconspicuously bi- 

 coloured, being a dull dark brown above and yellowish- white below ; 

 the fine hairs, which clothe it but do not conceal the skin, are blackish 

 above, whitish below. 



Barrett-Hamilton observed the moult in a specimen oi" hibernicus" 

 taken at Kilmanock on 3rd August 191 2. There is probably also a 

 spring moult ; O. Jones {^A Gamekeeper's Notebook, 26) says the coat 

 is rusty red then, especially if the rats are living in burrows in soil, and 

 if short of food or living on carrion, which delays the moult. It is 

 probable that all murines have distinct summer and winter coats. 



The pelage of the yoirng (soon after they have left their dam) does 

 not differ conspicuously from that of the adults : it is rather softer, 

 fuller, and duller in colour. The young are slenderly built ; their ears 

 relatively thin and, together with the tail and feet, relatively longer than 

 in the adults. On cursory examination they may easily be confused 

 with rattus, but all may be correctly determined by comparing their 

 proportions with those of rattus of similar age, apart from the quality 

 of the fur and the characters of the skull. 



Local variation: — William Thompson's {Proc. Zool. Soc, 1837, 

 52) description of the Irish Rat, Mus hibernicus, has given rise to a 

 bulky literature. It was supposed to be characterised by the possession 

 of white fore-limbs and of a white breast spot, but these have since 

 proved to be very variable characters, more frequently absent than 

 present, the chest spot when present being of various and often 

 asymmetrical shapes. Apart from these features, hibernicus differs 

 from ordinary brown specimens in the uniform dusky hue of the 

 complete pelage and the absence of a white underside ; and it is, in 

 this respect, parallel to melanisms of the rabbit. The skin also is 

 dusky, and a peculiarity is the frequent presence of numerous grey 

 hairs on the flanks, which give a very blue appearance. 



No doubt owing to its black colour, it was compared by Thompson 

 with E. rattus, and in Bell's 2nd edition it is mentioned by Tomes in 

 the article on that species. Others (as Southwell, Zoologist, 1889, 321, 

 and Trans. Norf. and Norw. N. H. Soc, ii., 419) have thought it a 

 hybrid. While fully cognisant of these errors, Eagle Clarke (in Harvie- 

 Brown and Buckley's Vert. Fauna of the Outer Hebrides, 1888, l6a) 

 was at first led to regard it as a distinct species, but later {Zoologist, 

 1891, i) he joined Barrett-Hamilton in describing it as an interesting 

 melanism of E. norvegicus, an opinion already expressed by Blasius 

 in 185;, and by de I'Isle in 1865 {op. cit., 189). The latter used 

 hibernicus, together with the melanistic races of House Mice, in 



