86 CALIFORNIA MAMMADS. 



'i'liey are fond of running along fallen trees, but I saw noije 

 climb standing trees. The number of young is unusually small, 

 two and three in a litter. These are born in the latter part of 

 May and in June. 



Genus Sciurus Linneus. (Shade — tail.) 

 Skull short, broad between the orbits; anteorbital foramen 

 \ery small; postorbital processes long, slender, bent obliquely 

 I aclward and downward; penultimate premolar very small or 

 absent; incisors narrow; inner toe on front foot very rudi- 

 mentary; ears large, sometimes tufted; tail long and bushy; no 

 internal cheek pouches ; mammae four to eight ; diurnal ; arboreal. 

 Dental formula, I, i — i; C, o — o; 2 — i or i — i; M, 

 3 — 3X2^22 or 20. 



Subgenus Hesperosciurus. 



Skull comparatively long, strongly arched in upper outline; 

 posterior part of cranium depressed ; rostrum long and deep ; 

 nasals long and narrow. 



Sciurus griseus Ord. (Gray.) 



COLUMBIA GRAY SQUIRREL. 



Size large ; general color of upper surface of head, body and 

 tail mouse gray thickly grizzled with white; e\e ring dull white; 

 ears in winter pelage clothed on the C(^n\-ex surface with s-nft 

 fur. dusky at tip, light brown at base, in summer scantily haired, 

 never tufted; no lateral stripe; under surface from chin to tail 

 white to roots of hairs, sharply defined against the ashen gray 

 sides; tail very large, long, bushy, flat, tlie hairs often three 

 inches long, slate gray mixed with whitish annulations, each 

 hair with a long white tip; under surface of tail pale ashv gray 

 centrally with blackish lateral bands and white border ; ashy grav 

 of shoulders and hips extending down on the outside of the 



