414 QUADRUMANA. 



tail ; in structural adaptation for an arboreal mode of life ; in intelligence 

 and docility, the accordance of the two groups is evident to the most 

 casual observer. The Gibbons, however, have their exclusive distin- 

 guishing characters, which draw a clear line of demarcation between them 

 and the preceding Apes, and justify the establishment of the genus 

 Hylobates. The presence of small ischiatic tuberosities (the commence- 

 ment, as it were, of that structural peculiarity which we find carried out 

 to its maximum among the inferior Simiadae), indicates a link of attach- 

 ment between them and the succeeding groups, and a move of one step, at 

 least, below the Orangs, in the scale of animated being. But the small- 

 ness of these callosities, and the circumstance of their being almost 

 hidden by the woolly fur with which the Gibbons are clothed, would seem 

 to militate against the attachment of much importance to them, as 

 regards their influence upon the habits of the animals. Probably the 

 Gibbons occasionally, or even habitually, rest, and also sleep, seated on 

 them, as do the lower Simiadae invariably.* 



The Gibbons differ from the thick-set Orang in the slenderness of 

 their form : the chest, indeed, is tolerably broad ; but the abdomen is con- 

 tracted, and the hips are extremely narrow ; the arms are of excessive 



Hand of Gibbon. 



length, reaching, in the erect attitude, to the ankle-joint ; and the hands (see 

 fig. 271) are remarkably long and slender ; the naked palm is linear, expand- 

 ing as it proceeds from the wrist ; the fingers are covered, down the backs, 

 with fur ; the thumb of the fore-hands resembles the fingers in form 

 and direction, and it is scarcely or not at all opposable to them ; it seems to 

 rise from the wrist, owing to the almost complete separation of its meta- 

 carpal bone from that of the first finger ; and the ball formed by its 

 adductor muscles is trifling. The feet are long, and their hinder thumb is 

 so greatly developed (see fig. 272) as to form an equal antagonist to 



* Mr. George Bennett, in his description of a Siamang, which he calls Ungka (a generic term for 

 the race), observes : " When sleeping, he lies along, either on the side or back, resting the head on the 

 hands. Frequently, when I awoke, I have seen him lying on his back, his long arms stretched out, 

 and with open eyes, appearing as if buried in deep reflection." Wanderings in New South Wales, $c. 

 vol. ii. p. 152. London: 1830. 



