52 WHAT EVOLUTION IS 



large as those of oxen. The fossil re- 

 mains of all these sloths and armadil- 

 los are found exclusively in the new 

 world and in that part south of the 

 central United States. It is a remark- 

 able fact that, notwithstanding the 

 great difference between these fossil 

 sloths and armadillos and their mod- 

 ern representatives, the living and the 

 fossil forms should agree almost 

 exactly in the regions where they 

 occur. One is forced to conclude from 

 facts of this kind, as well as from the 

 circumstance, that most well-defined 

 groups of modern animals, like the 

 monotremes and the marsupials, oc- 

 cupy definitely restricted areas, that 

 members of the same great group have 

 had a common origin, for had they 

 been specially created their distribu- 

 tion on the earth's surface would have 

 called for no particular regularity. 



