THE ANTERIOR LIMBS OF QUADRUREDS. 45 



extinct sloths, professor Owen thus expresses 

 himself : — " If the foregoing physiological in- 

 terpretation of the osseous framework of the 

 gigantic extinct sloths be the true one, they 

 may be supposed to have commenced the pro- 

 cess of prostrating the chosen tree by scratch- 

 ing away the soil from the roots ; for which 

 office we find in the mylodon, the modern scan- 

 sorial (climbing) fore-foot of the sloth modified 

 after the type of that of the partially fossorial 

 (digging) ant-eater. The compressed or sub- 

 compressed form of the claws, which detracts 

 from their power as burrowing instruments, 

 adds to their fitness for penetrating the inter- 

 spaces of roots, and for exposing and liberating 

 them from the attached soil. This operation 

 having been duly eftected by the alternate 

 action of the fore-feet, aided, probably, by the 

 ungiuculate (clawed) digits of the hind feet, 

 the long and curved fore-claws which are 

 habitually flexed (bent) and fettered in the 

 movements of extension, would next be applied 

 to the opposite sides of the loosened trunk of 

 the tree. And now the mylodon would derive 

 the full advantage of thost modifications of its 

 fore-feet, by Avhich it resembles the sloth ; the 

 correspondence in the structui'e of the prehen- 



