674. PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. XXXIV. 
Museum from the west coast of Sumatra to compare with the present 
series from Aru Bay, but the latter, for the present at least, may be 
regarded as undoubted specimens of Hylobates albimanus. 
As this name has for so long been placed as a synonym of Hylobates 
lar Vanneeus and not without cause (for none of the differential char- 
acters are brought out in the original description) I give below a 
description of the Aru Bay specimens and a comparison between 
them and a series of Whitehanded Gibbons from the Malay Peninsula. 
Color.—The general color of the body and the limbs is “ brown ” 
in varying shades. Top of head, limbs, and underparts of body very 
similar to Ridgway’s Prout’s brown, gradually hghtening over the 
shoulders, rump, and sides to a light Isabella color or wood brown. 
Upper surfaces of hands and feet dirty cream color. <A dirty cream 
color surrounds the face, most conspicuous back of the cheeks and 
under the chin. There is some variation in the intensity and in the 
extent of the “brown” colors. One specimen, Cat. No. 143567, 
U.S.N.M., male, is very light, almost dull cream color throughout, 
but the top and sides of head are wood brown, and the arms and legs 
incline toward that color. Cat. No. 143565, U.S.N.M., also a male, 
has the “ browns” more intense than most of series, thus bringing 
into stronger contrast the light hands and feet as well as the light 
colored band about the face. 
Skull—tIn the skulls of HZylobates albimanus the bony rim of the 
orbit is much less conspicuous than it is in Z/. lar. The difference is 
especially noticeable in the supraorbital region; the space between 
the inner angles of the supraorbital ridges is shallow in the Sumatran 
Whitehanded Gibbon, but in the Malaccan species a prominent fur- 
row is found between them. (Plate LIV, figs. la, 2a.) The nasal 
bones show almost a straight line from above downwards in /ylo- 
bates albimanus, while in ZH. lar they are decidedly concave from 
above downwards, thus making the profiles of the skulls of this species 
quite different. (Plate LIV, figs. 10, 2b.) The ascending por- 
tion of the mandible is very unequally developed in the two forms, it 
being much deeper in ZZ. Ja, about as deep as it is long, in Z/. albi- 
manus being very shallow and longer than it is deep. (Plate LIV, 
figs. 16, 2b.) In Hylobates lar the mental foramen lies in a broad 
shallow fossa on the side of the mandible. This fossa is quite 
lacking in 77. albimanus, and the foramen opens on a slightly convex 
surface. 
Teeth—The teeth of Hylobates albimanus average smaller than 
they do in ZH. dar. In the peninsular form the three upper molar 
teeth are of nearly the same size, the third in some individuals being 
a trifle smaller. In the Sumatran form the third upper molar is 
reduced in size and distinctly smaller than the subequal first and 
second molars. 
Measurements.—See table, page 675. 
