38*2 MONOGRAPH OF THE GENUS SCIURUS. 



enterprising journey over the Rocky Mountains. All of them 

 present the above dental formula, and if the species has, at 

 any time, the small deciduous front tooth in the upper jaw, 

 it must drop out at a very early period. 



The incisors are a little smaller than those of Sciurus Hud- 

 sonius. In the upper jaw, the anterior molar, which is the 

 smallest, has a single rounded eminence on the inner side ; 

 on the outer edge of the tooth there are two acute points, and 

 one in front ; the next two grinders, which are of equal size, 

 have each a similar eminence on the inner side, with a pair 

 of points externally ; the posterior grinder, although larger, 

 is not unlike the anterior one. In the lower jaw the bound- 

 ing ridge of enamel in each tooth forms an anterior and pos- 

 terior pair of points. The molars increase gradually in size 

 from the first, which is the smallest, to the posterior one, 

 which is the largest. 



This species, in the form of its body, is not very unlike the 

 Sciurus Hudsonius ; its ears and tail, however, are much 

 shorter in proportion, and in other respects, as well as in size, 

 it differs widely. 



Head considerably broader than that of Sciurus Hudsoni- 

 us ; nose less elongated and blunter; body long and slender; 

 ears rather small, nearly rounded, slightly tufted posteriorly. 

 As usual in this genus, the third inner toe is the longest, and 

 not the second, as in the spermophiles. 



Colour. — The whiskers, which are longer than the head, 

 are black. The fur, which is soft and lustrous, is, on the 

 back, from the roots to near the points, plumbeous, tipped 

 with brownish grey, with a few lighter-coloured hairs inter- 

 spersed, giving it a dark brown appearance; when closely ex- 

 amined, it has the appearance of being thickly sprinkled with 

 miuute points of rust colour on a black ground. The tail, 

 which is distichous but not broad, is for three fourths of its 

 length the colour of the back ; in the middle the fur is plum- 

 beous at the roots, then irregular markings of brown and black, 

 tipped with soiled white, giving it a hoary appearance ; on 

 the extremity of the tail the hairs are black from the roots, and 

 tipped with light brown. The belly, the inner sides of the 

 extremities, and the outer surfaces of the feet, together with 

 the throat and mouth, and a line above and under the eye, are 

 bright buff. The colours on the upper and under parts are 

 separated by a line of black, commencing at the shoulders, 

 and running along the flanks to the thighs. It is widest in 

 the middle by about three lines, and tapers off to a point. — 

 The hairs, which project beyond the outer margins of the ears 

 and form a slight tuft, are dark brown, and in some specimens 

 black. 



