172 HYLOBATES 
MULLER’S GIBBON. 
Type locality. Borneo. Type of S. concotor Harlan, not in 
Philadelphia Academy. 
Geogr. Distr. Borneo. 
Color. Top of head, black; back of head and upper parts of body 
variable, gray, buff yellow or dark broccoli brown, and in this case 
the upper back, hind neck and shoulders are nearly seal brown; arms 
usually the color of the upper parts, grayish, seal brown or wood 
brown, with black on inner side; legs gray, buff or seal brown; side 
of head and under parts of body black; inner side of thighs black; 
of legs, similar to back. | 
Measurements. Skull: occipito-nasal length, 88; Hensel, 74; 
zygomatic width, 62; intertemporal width, 47 ; median length of nasals, 
7; length of upper molar series, 24; length of mandible, 70; length of 
lower molar series, 28. 
This is a most changeable species and it is quite hopeless to attempt 
to recognize distinct forms among the variously colored individuals. 
The animals from the south-eastern and north-western sides of Borneo, 
have been separated as miilleri and concolor, on account of the former 
having darker hands and feet and under parts; but this distinction 
does not hold good, and in the British Museum are specimens with 
light and dark hands and feet taken in the same locality, and the under 
parts are black or brownish black. Color in this species, as in some 
others of the genus, has no specific value. 
The species has a gray phase, sometimes with a more or less 
distinct blackish cap and as this certainly has some resemblance to the 
Javan species, it was supposed that H. Lreuciscus inhabited both 
islands. In respect to this Mr. Hose’s testimony, given in his Mammals 
of Borneo, 1893, p. 60, of this species is interesting. He says, calling 
the animal H. miilleri, “this species varies from gray to dark yellowish 
brown, but the gray in certain lights appears pure ashy, and in others 
of a brownish tint. In some the chest and abdomen are frequently 
of a lighter color than the other parts, and of a brownish yellow, and 
this seems to be the character of individuals met with on the west 
coast of Borneo, while those inhabiting the meridional parts of the 
island have the hands and foreparts of the body of a black brown 
or reddish brown. In both of these varieties there is a yellowish 
white supercilium. The last of them leads into the Hylobates from 
the neighboring islands of Sulu to the northeast of Borneo, in which 
the upper parts of the body are either gray or brownish, the lower 
part of the back and loins being a little more clear than the rest. 
