WHAT EVOLUTION IS 51 



reptile than of a mammal, but its 

 warm blood, its mammary glands, and 

 the hair that projects outward be- 

 tween the segments of its shell pro- 

 claim it a true mammal. 



Modern sloths and armadillos are 

 limited to the new world particularly 

 to South and Central America though 

 the armadillos extend northward 

 through Mexico into the southern 

 borders of the United States. None 

 of these forms occur in the old world 

 or in fact elsewhere than in the region 

 just described. 



Fossil sloths and armadillos are 

 known in considerable numbers. Some 

 of these are of huge size. Fossil 

 ground sloths have been discovered 

 whose skeletons justify the belief that 

 the living animal must have been as 

 large as a rhinoceros. Armadillo- 

 like animals, the glyptodons, have been 

 found whose skeletons are almost as 



