SOME EXTINCT ARGENTINE MAMMALS 107 



the present day. Browsing on the leaves and perhaps the 

 smaller branches of forest-trees, the ground-sloths probably 

 obtained their food by rearing themselves up against the 

 trunks, supported on the tripod formed by their massive 

 hind-limbs and powerful tail, the ponderous structure of 

 the haunch-bones being eminently adapted for maintaining 

 the body in such a posture. The same massiveness of 

 structure conclusively proves that the creatures were not 

 arboreal, since no tree capable of being climbed could 

 carry such an enormous weight. It was suggested, indeed, 

 by Sir Richard Owen that the megalothere was in the 

 habit, when reared up in the manner indicated above, of 

 clasping a tree in its arms and swaying it backwards and 

 forwards until it fell with a crash to the ground ; but 

 although such a radical mode of procedure may have been 

 occasionally resorted to, we have no right to assume that 

 such was the ordinary habit of the ground-sloths. 



