S90 



MURID^— EPIMYS 



ts^ 



somewhat harsh quality to the fur ; on the back many of them are stifif, 

 broad, flattened bristles, each with a distinct groove along its anterior or 

 dorsal surface. In hot countries such hairs are in all rats frequently 

 developed as spines. On the back, and particularly towards the 

 rump, long black hairs, usually of from 20 to 25, but sometimes 30 or 

 40 mm. in length, occur ; although these long hairs are a good deal 

 more slender than many of the middle hairs, they also contribute 

 towards producing a certain looseness and harshness in the appearance 

 of the fur. 



Colour: — The colour ranges from uniform dusky to brown, with 

 a white or cream belly, and above it is usually darker along the dorsal 



line. Between the extremes every 

 intermediate gradation may be 

 found. These intermediates occur 

 frequently in large towns or ports, 

 where, owing to the cosmopolitan 

 nature of the rat populations of 

 such localities, much crossing prob- 

 ably takes place. In more open 

 and remote districts the coloration 

 conforms usually to one or more 

 definite types, and intermediates 

 are rare ; for details, see below 

 under Geographical variation. 



Young: — The pelage of the 

 young is relatively soft and full; 

 all three kinds of hair can be 

 distinguished in individuals with 

 a head and body length of from 

 78 to 100 mm., but the bristles 

 and long dorsal hairs in such 

 specimens are relatively feeble 

 and do not much exceed the 

 underfur in length. In the " wild- 

 coloured" races the coloration is 

 generally like that of the adults, although the hue is duller and greyer. 

 According to de ITsle, the dusky (r. rattus) and the "wild-coloured" 

 {frugivorus) races are distinguishable by colour ten days after birth. 



The adult skull (Fig. 90) compared with that oi E. norvegicus differs 

 in its smaller size (condylo-basal length 38 to 45 mm., instead of 43-4i 

 usually not less than 45, to 54-2 mm.) and lighter build. The brain-case 

 is relatively slightly broader; the prominent supra-orbital ridges are 

 continued backwards along the parietals, at a relatively low level, as out- 

 wardly curving (instead of approximately parallel) crests ; the length 



Fig. 90. — Skull and Mandible of Epimys 

 rattus (life size). From Miller's Catalogue 

 of Mammals of Western Europe ; reproduced 

 by the kind permission of the Trustees of 

 the British Museum (Nat. Hist). 



