sciuEus >^99 



tail (Icc'idtiilly inoro tliaii half as long as head and body ; car 

 conspicuously tufted in winter ; colour reddish, greyish or dark 

 brown above, whitish (never distinctly yellowish) below ; minute 

 anterior upj^er premolar present ; cross-ridges on U2:)per molars 

 smooth, not tending to become tuberculate ; lower incisors 

 extremely compressed. 



External characters. — Form slender, the head and neck well 

 differentiated from the trunk, the legs rather long, the tail about 

 Cijual to head and body. Head rounded posteriorly, narrowed in 

 front, the muzzle deep and not much produced (distance from eye 

 to nostril about equal to depth at I'egion half way between) ; ear 

 rather large, just covering eye when laid forward, the A\'idth at 

 middle about three-quarters height from crown ; anterior bortlei- 

 nearly straight below, somewhat convex above, its lower two- 

 thirds abrujjtl}^ folded backward, the inner root of this fold lying 

 uearly over meatus ; tip rather abruptly rounded ofl"; posterior 

 border convex except for a flattened or slightly convex region 

 just below tip, its lower border extending forward as an abruptly 

 angled j^i't'jection over meatus ; outer surface of ear densely 

 furred at all seasons, the tip conspicuously tufted in winter 

 pelage ; muzzle pad hairy above, a narrow bare area extending 

 between nostrils and across upper lip and sending out a 

 lateral branch under each nostril. Fore feet long and slender 

 with long, freely spreading lingers ; thumb reduced to a mere 

 tubercle with closely appressed nail ; two middle lingers sub-equal 

 and longest, second and lifth svib-ecjual and about half as long ; 

 palm with Ave tubercles, the two posterior lai'gest and best 

 deflned ; claws long, compressed, strongly curved. Hind foot 

 long, the Ave toes all well developed and bearing strong claws 

 shorter and less curved than those of fore foot ; inner toe 

 extending about to base of others, outer extending a little beyond 

 middle of foui'th ; fourth toe longest, third and second successively 

 a little shorter ; sole densely hairy in winter, jjartly bare in 

 summer ; four small but evident tubercles at bases of toes. Tail 

 strictly tlistichous throughout, the hairs at sides and above about 

 30 to 50 mm. in length. Mammae, p 1 — 1, a 2 — 2, i 1 — 1 = 8. 



Colour. — Though the actual colour shows great diflerences 

 according to phase and season the pattern is constant and 

 charactei'istic. The head, back, sides and tail ai'e essentially 

 uniform, the tail usually a little darker than back, the sides of 

 body and outer surface of limbs somewhat lightei', the middle of 

 back fi'equently with more I'ed ; face with an ill-defined j^ale area 

 on cheeks and muzzle ; ear-tufts usually concolor with sur- 

 rounding parts but sometimes dai'ker or more red ; inner surface 

 of legs and upper surface of feet not so dark as outer surface of 

 legs ; tail with a lighter, grizzled or whiti.sh area along median 

 line below, this sometimes pai'tly or wholly concealed ; white of 

 iniderparts extending forward to chin or to back of interramial 

 space; posteriorly the white does not reach base of tail, and 



