8 SIMIID^. 



guisliably the peculiar "Wow Wow" of the former, both in its slow and in its 

 remarkably rapid, trilling scale. 



Hylobates mulleri, Martin. 



Hi/lobates concolor,Mvi\\er,YQx\i&\id\. OYQX d,Q Zool. ind. Archipel, 1841, p. 48; BIyth, Joura. As. 



Soc. Beng. vol. x. 1841, p. 838; Martin, Nat. Hist. Quadr. 1841, p. 417; ScliiEZ, Syn. Mamm. 



vol. i. 1844, p. 31 ; Temminck, Coup d'oeil sur les Possess. Neerland. vol. iii. 1849 p. 403; 



Hist. Nat. des Mammif. 1854, p. 55 (fig. of head); Wagner, Sckreber, Saugeth. Suppl. vol. v. 



1855, p. 17 (in part). 

 Hylobates milllen, Martin, Nat. Hist. Quadr. 1841, p. 444 ; Temminck, Coup d'oeil sur les Possess. 



Neerland. vol. iii. 1849, p. 403 ; Is. Geofi". St.-Hil. Cat. Me'thod des Mammif. 1851, p. 7 ; 



Arch, du Mus. vol. v. 1852, p. 534; Dahlbom, Stud. Zool. Fam. Reg. An. 1856, pp. 73, 75. 

 Eylolates funereus, Is. Geoff. St.-Hil. Compt. Rend. vol. xxxi. Dec. 1850, p. 874; Cat. Method, des 



Mammif. 1851, p. 7; Arch, du Mus. vol. v. 1852, p. 532, pi. xxvi; Gervais, Hist. Nat. des 



Mammif. 1854, p. 53, figure; Wagner, Schreber, Saugeth. Suppl. vol. v. 1855, p. 18. 



This species varies from grey to dark yellowish brown, but the grey in certain 

 lights appears pure ashy, and in others of a brownish tint. In some the chest and 

 abdomen are frequently of a lighter colour than the other parts, and of a brownish 

 yellow, and this seems to be the character of iudividuals met with on the west 

 coast of Borneo, while those inhabiting the meridional parts of the island have the 

 hands and fore part 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 neighbouring islands of Sulu to the north-east of Borneo, in 

 which case the upper parts of the body are either grey or brownish, the lower part of 

 the back and the loins being a little more clear than the rest. The outer surface of 

 the limbs, the feet, less the toes, the back part of the head, a narrow supraorbital 

 band, and the sides of the face, are paler than the other parts, and generally are ashy 

 grey, more or less pure. The anterior portion of the upper surface of the head and 

 the ventral aspect of the body are more or less brownish black, and the inner 

 aspect of the limbs is of the same tint in the greater part of its extent. The upper 

 surfaces of the hands and the toes are of the same colour, but the blackish brown is 

 markedly mixed with grey. The face and under parts are black and the eyes are 

 brown. 



Inhabits Borneo and the neighbouring islands of Sulu. 



As has been remarked by Miiller, this species is closely allied to H. leuciscus, 

 the general type of colouring being the same in both ; and this observation is also 

 applicable to S. pileatus, and in a more modified degree to S. agilis, all of these 

 Gibbons being characterised by the tendency to form a dark skull-cap, so to speak, 

 and by the colour of the dorsal region to pale on the loins ; while in H. mulleri and 

 J3". pileatus there is the further disposition for the breast, belly, and inside of the 

 limbs to become darker than the back ; but as this is also the character of the light- 

 coloured females of S, hoolocTc, much specific importance cannot be attached 

 to it. 



