804 RODENTIA 



castwurd, ;ui(l fi'oin contral Sweden and Norway soutli to 

 iiortheT-ii Italy and the soiitliern I'^ranct; ; Iceland (probably 

 introduced). 



Diagnosis. — Size small ; head and body, about 95 ; tail 

 vertebrae, about 90 ; hind foot, about 22 ; condylobasal length of 

 skull, 22 to 24 '6 mm. ; general colour of upper parts relatively 

 dark and rich, the sides and flanks a russety, yellowish, wood- 

 brown. 



Colour. — Ordinary adult specimens in fresh pelage are wood- 

 brown above, distinctly tinged with russet on posterior half of 

 back, and becoming paler and more bufty on head, neck, 

 shoulders and sides ; everywhere there is a noticeable sprinkling 

 of blackish hairs, these usually producing a decided effect of 

 " lining," and over middle of posterior half of back a slight 

 though evident dark clouding ; cheeks, sides of neck, outer 

 surface of fore legs and a narrow, ill-defined region along hne 

 of demarcation, dull light buff; uuderparts and dorsal surface of 

 feet dull white, the throat and belly always clouded by the slate- 

 grey undercolour, and not infrequently with a slight or decided 

 buffy wash ; chest usually with a buff median area between fore 

 legs, this occasionally forming a complete collar or spreading 

 backward along median line ; ear dull brownish with no decided 

 markings, the edges usually lighter and often faintly silvery ; 

 tail bicolor, though in most specimens not conspicuously so, the 

 upper surface dark brown, the under surface whitish. Immature 

 individuals are duller than the adults, the upper parts usually 

 with a plumbeous tinge, the underparts more slaty, so that there 

 is occasionally no well marked line of demarcation along sides. 

 Specimens in this pelage often resemble some of the bicolored 

 forms of the 3Ius miisciiJus group, though they may always be 

 distinguished by their relatively larger eyes and ears, relatively 

 longer hind foot, and by the absence of supplementary tubercles 

 to all of the pads on sole. 



Measurements. — Two adult males from Iceland : head and 

 body, 90 and 95; tail, 87 and 92; hind foot, 22-6 and 23-2; 

 ear, 18 and 17 '6. Average and extremes of five adults from 

 Ireland: head and body, 97 (90-103) ; tail, 83-7 (71-97) ; hind 

 foot, 22-3 (22-23); ear from meatus, 15-5 (15-16). Average 

 and extremes of ten adults from the Isle of Man : head and 

 body, 95 (90-103); tail, 84 (75-93); hind foot, 22-2 (21-23); 

 ear from meatus, 16 (15-17). Average and extremes of five 

 adults from Cromarty, Scotland : head and body, 95 '6 (92-101) ; 

 tail, 87-2 (83-91); hind foot, 22-6 (21-23); ear from meatus, 

 16 "8 (16-17). Average and extremes of ten adults from 

 Wormsley, Oxfordshire: head and body, 96 "5 (90-105); tail, 

 90-1 (79-99); hind foot, 22-1 (21-23). Average and extremes 

 of six adults from Tresco, Scilly Islands, Cornwall : head and 

 body, 95-5 (92-99); tail, 88 (83-96); hind foot, 22-2 (21-23): 

 ear from meatus, 15 5 (15-16). Average and extremes of ten 



