50 WHAT EVOLUTION IS 



This topic is still better illustrated 

 if we take into consideration the 

 distribution of fossil, as well as of 

 living forms. Again the mammals 

 may serve as illustrations. Sloths and 

 armadillos constitute a group of mam- 

 mals very striking in their distribu- 

 tion. 



The modern sloths are arboreal 

 creatures of moderate size; they feed 

 upon the succulent stems and leaves 

 of tropical trees. By means of their 

 curved claws, they hook themselves 

 through the tangle of branches in the 

 forest jungle. They are almost in- 

 capable of locomotion on the ground 

 and when by accident they fall, they 

 move about in a most awkward fash- 

 ion in regaining their haunts. 



The modern armadillo is a burrow- 

 ing animal chiefly active at night. Its 

 covering of segmented shelly pieces 

 gives it more the appearance of a 



