321 



one cream-buff sub-terminal annulation, producing a noticeably 

 speckled appearance throughout dark area ; flanks with a few 

 long, entirely buff hairs ; sides of body and of neck light cream- 

 buff tinged with clay-colour, in striking contrast with dark areas, 

 the buff lateral area divided at shoulder by band about 60 mm. 

 wide where drab of back crosses to leg ; anteriorly the buff 

 lateral area extends to about level of ears where it abruptly gives 

 place to dark brown of head ; inner surface of ear light buffy 

 grey ; underparts and inner surface of legs buffy greyish, slightly 

 contrasted with sides ; under surface of tail like sides of body, 

 upper surface essentially like back at base (where line of 

 demarcation is well defined), but becoming tinged with buffy 

 toward tip. Winter pelage : entirely white, tinged with yellowish 

 on throat, neck and face ; underfur and posterior surface of ear 

 light drabby grey. In the " blue " phase the entire animal is at 

 all seasons a bluish drab, usually washed with sepia on head and 

 feet, and sprinkled with pure white hairs on face, chin and throat. 



Skull.- — The skull is shorter and narrower than that of VuJpes 

 vulpes, but of nearly equal depth, a difference in form due in part 

 to the greater elevation of the interorbital region and in part to 

 the relatively greater depth of brain-case (depth equal to one- 

 third condylobasal length instead of noticeably less as in 

 F. vulpes) ; muzzle less produced 

 than in the common fox and rela- 

 tively wider proximally ; zygomata 

 less abruptly spreading anteriorly, 

 so that the region of greatest 

 zygomatic breadth is noticeably at 

 glenoid level. In other respects 

 there is essential agreement with 

 the skull of F. vulpes. Anteorbital 

 foramen over space between pm^ 

 and pm'^ ; auditory bulla relatively 

 as large as in the larger animal ; 

 depth of brain-case through bulla 

 equal to greatest breadth above 

 roots of zygomata ; postorbital pro- 

 cesses slightly less concave on 

 underside and somewhat more 

 flattened above ; mandible with 

 ramus relatively a little deeper 

 and more compressed than in the 

 common fox. 



Teeth. — In general the teeth 

 closely resemble those of Vulpjes 

 vulpes except for their slightly 

 smaller size. Incisors both above 

 and below with relatively wider crowns than in the common fox, 

 the cingulum of i^ and «"- much more developed and forming a 



Fig. 64. 

 Alopcx lagopus. Teeth. 



