6i2 MURID^— EPIMYS 



than is E. rattus, and in a somewhat different direction. While rattus 

 is essentially fitted for a free, semi-arboreal life, norvegicus has pursued 

 a more earth-bound course. It has acquired accordingly a stouter and 

 heavier body, a shorter tail, and its structure, in many points, has 

 suffered modifications adapting it for burrowing, swimming, and the 

 other activities incidental to its peculiar mode of living. 



Description : — Though generally resembling E. rattus in form, the 

 Common Rat is characterised by its relatively large size, great weight, 

 robust form, short, thick ears, and by its shorter tail, which is never as 

 long as the head and body. 



The snout is relatively blunt. The eyes are small, though some- 

 what larger than in rattus. The ears are short, about one-third as long 

 as the head and scarcely reaching the eyes when laid forward ; their 

 substance js thick and opaque, and they are clothed with fine short 

 hairs ; in young animals they are relatively large and thin. The 

 bands and feet are much like those of rattus, although more robust ; 

 the fingers and toes have similar proportions, and the number and posi- 

 tions of the palmar and plantar pads are essentially the same in both 

 species. The pads, especially those of the sole, are, however, relatively 

 small in norvegicus ; in the hand and foot there is sometimes a small 

 free pad external to that at the base of digit 5 ; and in the foot another 

 is occasionally present, to the inner side of that at the base of digit i. 

 The tail differs from that of rattus in being shorter and stouter, while 

 the annulations are masked to some extent by the greater distinctness 

 of their component scales ; it has about one hundred and eighty rings 

 in all, and a few small hairs rise from beneath each scale. The female 

 has twelve mammae, arranged as two pectoral, one abdominal, and three 

 inguinal pairs. 



Pelage : — The underfur is thick. The grooved bristles are much 

 finer and present in much fewer number than in rattus, the long black 

 dorsal hairs are shorter ; in consequence of these differences the fur as 

 a whole is rather softer and less harsh in quality than that of rattus, 

 but the greater length of the underfur imparts a rougher and shaggier 

 appearance, particularly noticeable on the belly, than that of £. rattus 

 rattus. 



The whiskers are relatively short, not extending beyond the ear 

 when pressed backward ; the lower ones are whitish, the remainder 

 black in colour. 



In the typical form the colour is darker on the back, where the tips 

 of a greater or less number of the hairs are black, and lightens towards 

 the sides, where dirty yellowish or whitish hair tips predominate. The 

 general tone of the upper parts is a very variable greyish-brown, lined 

 with black, and with an occasional reddish tinge over the rump and 

 loins. The underside is variably lighter, the colour of the belly varying 



