84 NELSON 



dingy yellowish brown; basal patches small, dingy gray or yellowish 

 gray ; sides of head finely grizzled gray, more whitish than back ; 

 ring around eye white, poorly defined ; underparts white ; tail above 

 black with a thin wash of white ; below, with broad median area dark 

 grizzled gray, a rather poorly defined black border, and thin white edge. 

 Hairs on back mostly black, with from one to three rings of white or 

 yellowish, intermixed with others entirely black. 



Variation. — The large series examined shows but little individual 

 variation. Winter specimens from northern California are somewhat 

 darker, more iron gray above, with much less black on upper 

 surface of tail so that the underlying gray shows through ; the ears are 

 more hairy and inclining to rusty on backs and basal patches. 



Measurements. — Average of five specimens from the Columbia 

 River region — near type locality of S. griseus : total length 569 ; 

 tail vertebrae 270.6; hind foot 81.8. Average of five adults from San 

 Diego Co., California — topotypes of '' anthonyi' : total length 566; 

 tail vertebrae 284; hind foot 80. 



Cranial characters. — Premolars ^. Skull (pi. I, fig. 5 ; pi. II, 

 fig. 4) rather long, tapering anteriorly; nasals long, narrowed 

 posteriorly; posterior part of the braincase inflated; audital bullae 

 small ; postorbital process of malar usually ending in a well developed 

 point. Molars unusually massive and the peg-like second premolar 

 stouter than usual. Skulls from the type locality of S. griseus 

 '• anthonyi' ^w&ra^Q a little smaller than those from the Columbia 

 River region, but the range of individual variation from the two 

 localities is such that it is impossible to find any definite subspecific 

 characters. Five adult skulls from near the type locality in the Colum- 

 bia River region average : basal length 58.3 ; palatal length 32.1; inter- 

 orbital breadth 20.8; zygomatic breadth 38.7; length of upper molar 

 series 12.9. Five adult skulls from type locality of S. griseus 

 anthonyi average: basal length 56.3; palatal length 30.2; inter- 

 orbital breadth 20.9; zygomatic breadth 37.7; length of upper molar 

 series 11.7. 



General tzotes. — Ord's S. griseus is based on the ' Large Gray 

 Squirrel' of Lewis and Clark, which is said to have been found in a 

 narrow tract of country well covered with white oak timber on the 

 upper side of the mountains just below ' Columbia Falls.' From 

 Lewis and Clark's narrative and the well known character of the coun- 

 try it is evident that the place referred to is near The Dalles of the 

 Columbia, which fixes the type locality with some certainty. 



A careful comparison of the type and topotypes of ' S. fossor an 



