MEGATHERIUM. 123 



origin of muscles, concerned in the movements of the foot. 

 Tiie radius (m) revolves freely on the ulna, as in the Sloths 

 and Ant-eaters, both of which make much use of the fore- 

 leg, though for different purposes ; it has a cavity at its up- 

 per end, which turns upon a spherical portion of the lower 

 part of the humerus, and a large apophysis (n,) projecting 

 from its longitudinal crest, indicates great power in the 

 muscles that gave rotatory motion. 



The entire fore-foot must have been about a yard in 

 length, and more than twelve inches wide ; forming a most 

 efficient instrument for moving the earth, from that depth 

 within which succulent roots are usually most abundant. 

 This great length of the fore-foot, w^hen resting upon the 

 ground, though unfavourable to progressive motion, must 

 have enabled one fore-leg, when acting in conjunction with 

 the two hind-legs and tail, to support the entire weight of 

 the body ; leaving the other fore- leg at liberty to be employed 

 exclusively in the operation of digging food.* 



The toes of the fore-foot are terminated by large and 

 powerful claws of great length ; the bones, supporting these 

 claws, are composed partly of an axis, or pointed core, (o,) 

 which filled the internal cavity of the horny claw; and 

 partly of a bony sheath, that formed a strong case to re- 

 ceive and support its base. These claws were set obliquely 

 to the ground, like the digging claws of the Mole, a position 

 which made them instruments of greater power for the pur- 

 pose of excavation. 



* At PI. 5, beneath Fig. 1, are represented the fore-foot of. an Armadillo 

 (Daspyus Peba,) and the forefoot of the Chlamyphorus, eacli adapted, like 

 that of the Megatherium, to form an instrument of peculiar power for the 

 purpose of dig-g-ing^; and each presenting an extraordinary enlargement 

 and elongation of the extreme bones of the toes, for tlie support of long and 

 massive claws. At PI. 5, Figs. 18, 19, the anterior parts of tliesc animals 

 are represented, and show how large a proportion the claws bear to the 

 other parts of the body. 



