388 ZOOLOGY. 



416. Classification of Reptiles. 



Order I. Chclonia {Turtles and Tortoises). The Chelonia are reptiles 

 with short, flattened or dome-shaped bodies enclosed in a case formed 

 by a dorsal shield (carapace) and a ventral (plastron). The jaws are 

 covered with a horny case and are destitute of teeth. The quadrate bone 

 is firmly fused to the cranium. The sternum is absent. Turtles seem 

 rather more common in the northern hemisphere. The largest species are 

 marine and may attain a weight of half a ton. Some live in fresh water 

 and others on land. The flesh of some species is much prized for food. 

 The green-turtle of the Atlantic coast is one of the choicest, its flesh 

 being much used for soups. The large hawkbill-tnrtle of the tropical seas 

 furnishes " tortoise-shell," used in combs and other ornaments. The 

 shells of the leather-back and other " soft-shelled " turtles are not com- 

 pletely ossified. The " snappers " are ferocious animals, the big snapper 

 of the Southern states being particularly vicious. 



FIG. 194. 



FIG. 194. Common Box Tortoise (.Cistudo Carolina). Photographed from life by 

 Dr. R. W. Shufeldt. 



Order II. Lacertilia (Lizards). Reptiles in which the body is usually 

 covered with small scales. Two pairs of limbs are ordinarily present ; 

 but either or both may be wanting. The quadrate bone is somewhat 

 movable. The teeth are not in sockets of the jaw. Sternum present. 

 The cloacal opening is transverse. 



The Lacertilia include, beside the types commonly known as lizards, 

 the chameleons, horned-toads, and the glass snake a legless lizard. They 

 subsist largely on insects and the eggs of other animals. Only one species 

 is known to be poisonous the " Gila monster " of New Mexico and 



