352 Professor Owen on 



diminishes the force of the argument which Cuvier de- 

 duced from the coalesced condition of the bones in the 

 Megatherium in favour of its affinities to the Armadillos. The 

 semi-inverted but firm interlocking articulation of the hind 

 foot to the leg shows the peculiarities of that joint in the Sloths 

 exaggerated, and departs further from its characteristics in 

 other Edentata. In all the existing Edentata, save the Sloths, 

 the hind foot is pentadactyle, and four of the toes have a long 

 claw, even in the little arboreal Myrmecophaga didactyla ; the 

 departure by degradation from the pentadactyle type is a pecu- 

 liar characteristic of the Sloth tribe in the order. It is carried 

 further in the same direction in the great extinct terrestrial 

 Sloths. In these the mutilation of the foot has commenced 

 on the outer side by the removal of the ungual phalanx from 

 the fifth and fourth toes ; but this accompanied by modifica- 

 tions which adapt these toes to the important office of support 

 and progression of the body on level ground. In the scansorial 

 Sloths, the three middle digits being equally developed for 

 prehension, one toe on the outer and one on the inner side 

 of the foot are reduced to their metatarsal basis. In the 

 Megatherium, the mutilation of the foot on the inner side is 

 carried to a greater extent ; the innermost toe, or hallux, 

 with its entocuneiform bone, is wholly removed ; the second 

 toe is represented, like the first in the Sloths, by its cunei- 

 form bone and a coalesced rudiment of the metatarse ; and it 

 is only the third toe, or medius, that repeats the condition of 

 the claw-bearing toes in the climbing Sloths. 



Habits and Food of the Megatherium. 

 Finally, the Professor enters upon the question of the 

 habits and food of the Megatherium. Guided by the general 

 rule that animals having the same kind of dentition have the 

 same kind of food, he concludes that the Megatherium must 

 have subsisted, like the Sloths, on the foliage of trees ; but 

 that the greater size and strength of the jaws and teeth, and 

 the double-ridged grinding surface of the molars in the Me- 

 gatherium, adapted it to bruise the smaller branches as well 

 as the leaves, and thus to approximate its food to that of the 

 Elephants and Mastodons. The existing Elephants and the 

 Giraffe are specially modified to obtain their leafy food ; the 



