442 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.xxxii. 



eyes, sides of neck and body, upper part of thighs, and upper part of 

 forearm a grizzle of russet and dark brown, the former color more con- 

 spicuous; underparts, inner side of legs, sides of head and region about 

 nose, inner side of ear and spot on thigh, white or nearly so ; lower leg 

 and arm a rather bright russet, and feet dull russet; tail seen from 

 above concolor with lower back, seen from below whitish in the mid- 

 dle line, but at tip and margin same color as it is above. There is a 

 marked contrast in color between the sides and underparts. Border- 

 ing the wliite underparts, the russet of the sides forms a bright and 

 clear line, with scarcely any admixture of brown. The fringes on the 

 fore and hind legs are bright clear russet. In worn pelage, the upper 

 parts become dull wood-brown or clay-color. Similar changes take 

 place in Ihe tail. 



Skull and teeth. — The skull and teeth of Ratufa hypoleuca show no 

 special characters; they are large like those of the form from Aru Bay, 

 and much smaller than those of R. imlliata. 



Measurements. — See page 445. 



Specimens examined. — Seven from Tarussan Bay and two from 

 Gunong Sugi. 



Remaj'lcs. — Ratufa hypoleuca is probably confined to the western 

 side and highlands of Sumatra, while in the swamp lands of the east 

 side it is replaced by a related form, and in the northern portion of the 

 island still another form of it occurs. (See map, Plate XXXIII.) 



RATUFA ARUSINUS, new species. 



Type.— Adult male, skin and skull. Cat. No. 143351 U.S.N.M., 

 collected at Aru Bay, northeast coast of Sumatra, January 16, 1906, 

 by Dr. W. L. Abbott. Original number, 4635. 



Diagnostic characters. — Similar to Ratufa hypoleuca, but underparts 

 dark buff, instead of wliite ; fore and hind feet dark brown, instead of 

 concolor with legs; and wliite markings about the head less con- 

 spicuous. 



Color. — Upper parts of head, neck, and body, sides of body, and 

 outer sides of forelegs a fine grizzle of a color between buft' and raw 

 sienna, and one similar to Front's brown, the former color in excess 

 anteriorly and on the sides, the latter in excess posteriorly in the mid- 

 dle line. Entire underparts, inner and outer sides of hind legs, inner 

 side of forelegs, and fringe on outside dark buff or ocliraceous buff. 

 Spot on tliigh cream-buff or whitish. Fore and liind feet a very dark 

 mummy brown, containing here and there a few scattered raw sienna 

 hairs. Cheeks and small area about the mouth dirty whitish, irregu- 

 larly lined with some light and dark brownish hairs. The whitened 

 area on the head is much less extensive than it is in R. hypoleuca and is 

 not found on the forehead between the eyes. Tail seen from above a 

 very dark brown, similar to Ridgway's seal brown; below, the outer 



