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. 
