-TJS 



ZOOLOGY. 



Reptiles are divided into three orders : chelonian, saurian, 

 and ophidian. 



The chelonian (tortoise and turtle) have four limbs ; the 

 skin covered with large scales; the mouth without trrth ; 



Fig. 289. The Agame. 



the jaws provided with a horny bill or covering; the ribs 

 immovable, and in them we find the horny dorsal and ven- 

 tral plates called carapace and plastron, already described. 

 The saurian or lizard-shape dreptiles, and the ophidians or 



Fig. 290. Crotilus, or Battlesnake. 



serpents, have the ribs and dorsal vertebrae moveable ; a scaly 

 skin ; and teeth. The two orders run into each other, but 

 it is generally agreed on to call those with limbs, saurian, and 

 those without, ophidian : as ophidian may be cited the viper, 

 rattlesnake (Fig. 290), cobra (Fig. 271), as venomous ; and 



