SKELETON OF BRUTA. 



411 



scansorial didactyle Anteater, in which a supplementary bone on 

 the inner (tibial) side of the tarsus is produced backward to 

 increase the power of the heel in grasping. 



In the Ai, fig. 264, the scapula, 5i, is broad, and its outer 

 surface is equally divided by the spine, which is short, but con- 

 tinued into an acromion arching to join the coracoid. The supra- 

 spinal notch is converted into a foramen by the extension of 

 ossification from the superior costa to the base of the coracoid. 

 The same characteristics are reproduced in the scapula of the 

 Megathere, fig. 279, 52, under more massive proportions of these 

 growths for muscular attachments, and with the superaddition of 



279 



Megatherium amcricanum. 



an inferior spine, as in the Anteater. The clavicle is complete in 

 the Megathere, ib. 58, as in the Two-toed Sloth ( Choloejms) : in 

 the Ai it exists as a short appendage to the acromion. In the 

 small climbing Sloths the length of the prehensile fore-limbs is 

 attained by that proportion of the humerus, fig. 264, 53, and 

 antibrachial bones, 54, 55 : both the latter are bent, leaving a 

 wide interosseous space, and are so articulated as to allow of 

 pronation and supination. In the Megathere the humerus is 

 relatively shorter, but thicker, and is enormously expanded at its 

 distal end, fig. 279, 53 : the inner condyle is imperforate, as in 

 Bradyims tridactylus : in the Megalonyx it is perforated as in 

 the Brad. {Cholceims) didactylus. The ulna of the Megathere, 

 fig. 279, 55, is equally remarkable for the vast expanse of its 



