544 



ANATOMY OF VERTEBKATES. 



In the Long-armed Apes {Hylohates, fig. 180) both acromion 

 and coracoid are large, and much produced. The clavicles are of 

 unusual length, equalling the extent of the eleven anterior dorsal 

 vertebrae. The bones of the arm and fore-arm are still more 

 remarkable for their length and slenderness, as well as those of 

 the fino-ers of the hand, the thumb of which is comparatively 

 short and slender. The femur is long and nearly straight. The 

 tibia is slightly bent. The thumb of the hind-foot is strong and 

 well-developed, with two phalanges. 



The great length of the pectoral limbs, and the provision made 

 for the extensive origin of some of their muscles by the breadth 

 of the thorax and the size of the scapulae and clavicles, relate to 

 the chief share which these limbs take in the rapid and character- 

 istic locomotion of this species, which swings itself thereby from 

 branch to branch, with a force that propels the body through 

 considerable distances. 



The Siamang offers the peculiarity of a common tegumentary 

 sheath of the proximal phalanges of the second and third digits 

 of the hind-hand, whence the name {Hyl. syndactylus). 



In the Orangs (Pithecus) the clavicle is less curved than in 



361 



Carpus of the Oraiig. lxix- 



Man, and the distal end is less expanded. The scapula approaches, 

 by its breadth, to the form of that of Man, but the acromion is 

 narrower, longer, and more antroverted. The humerus, in some 

 Orangs, shows a small perforation between the condyles. The 



