222 VERTEBRATA 



The crocodilians reproduce by laying from thirty to 

 sixty oblong white eggs as large as those of a hen, in a 

 mound of muck, vegetable mold, or sand. Sufficient 

 heat to hatch them is furnished by the sun and the fer- 

 mentation in the decaying mound. The young of our 

 species are more than six inches long when born. 



Chelonia or Testudinata: Tortoises and Turtles 



The members of this order are characterized by a more 

 or less fully developed bony shell investing the body and 

 by the absence of teeth. 



They are widely distributed throughout the warmer 

 regions of the globe, about fifty species being known in the 



United States. 



The name tortoise 

 is applied to those 

 forms having strong 

 legs with unwebbed 

 feet adapted to pro- 

 gression on land. 

 The commonest rep- 

 resentatives east of 

 the Rocky Moun- 

 tains are the box 

 tortoise ( Terrapene 



FIG. 258. Box tortoise seen from beneath to show Carolina) and the 

 the hinge joint. One fifth natural size. Photo- Wf)od tOTtOlSB (Clem- 

 graph by D. S. Hartline. 



mys insculpta). In 



the box tortoise the dorsal shell, called carapace, is strongly 

 arched and of variable colors, blackish and yellowish. 



