no. 1809. MAMMALS FROM BORNEO AND VICINITY— LYON. 



143 



Diagnostic characters. — A geographic race of Hylobates mulleri 

 distinguished from the typical form by lighter crown patch, light- 

 colored chin and side whiskers, and the lower back very much lighter 

 in color than rest of upper parts. 



Color. — Type: Narrow rim of hairs encircling face blackish, fol- 

 lowed by a narrow, dirty white forehead band, widening and the 

 individual hairs lengthening to form well-marked side whiskers and 

 a whitish patch on throat; crown patch dark-drab color; anterior 

 portion of back and sides, including adjacent portions of arms, a sort 

 of drab gray; posterior portion of back and sides, pale cream buff; 

 underparts, a blackish brown, continuous with the seal-brown color 

 of the inner side of the arms and legs; dorsal surfaces of hands and 

 feet blackish or blackish brown; outerside of forearms and legs a 

 sort of light clay or light isabella color. The colors everywhere are 

 subdued and there are no abrupt changes from one color to the next. 

 The main distinguishing color character between the gibbons of 

 southeastern and southwestern Borneo are shown in the table below. 



Gibbons from southwestern Borneo, Hylobates 

 mulleri albibarbis. 



Gibbons from southeastern Borneo, Hylobates 

 mulleri mulleri. 



Crown patch dark brown. 



Lower half of back, generally light buffy in color, 



and arms inclining toward same color. 

 Side and chin whiskers buffy in six out of nine 



specimens, brownish in the other three. 

 Underparts, including inner side of legs and arms, 



blackish brown, less widely diffused. 



Crown patch blackish. 



Lower half of back, generally wood brown in color, 



and arms inclining toward same color. 

 Side and chin whiskers brownish, not conspicuously 



different in color from rest of animal. 

 Underparts, including inner side of legs and arms, 



blackish, widely diffused. 



Skull and teeth. — I have been unable to find any characters by 

 which to distinguish the skulls or teeth of the gibbons of one part of 

 Borneo from those of another part of the island. 



Measurements. — For external and cranial measurements of the 

 type and series see table, page 144. 



Specimens examined. — Ten, from various localities in southwestern 

 Borneo. (For exact localities see table of measurements, p. 144.) 



Remarks. — The gibbons of Borneo, as shown by Doctor Abbott's 

 specimens, are all closely related, as is indicated in part by the lack 

 of distinguishing characters in the skulls. Hylobates leuciscus, while 

 very different in coloration from H. mulleri, is evidently not distantly 

 removed. It possesses a light-colored forehead band and shows a 

 darkening of the fingers and toes, but none of the specimens show an 

 indication of the dark crown patch. It is not improbable that some- 

 where in Borneo the two forms intergrade. Doctor Abbott failed to 

 indicate from which side of the Kapuas River his specimens were 

 taken, but they probably came from the north bank, so that the 

 Kapuas serves as a barrier between the two forms, as it does in the 

 case of the prevostii group of squirrels. Intergradation should be 

 looked for in the interior of the island near the sources of the Kapuas. 



