REPTILIA 



393 



toise-shell are used in the manufacture of bags, ornaments, and 

 the Hke. 



Probably the chief value of the group to man is in the de- 

 struction of noxious insects by lizards and rodents by snakes. 



425. Classification of Reptiles. 



Order I. Testudinata {Turtles and Tortoises). — The Testudinata are reptiles 

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

 shield {carapace) and a ventral {plastron). In some the carapace and plastron 

 make a rather tight-box practically covering the animal. In others they are 

 smaller and the edges are further apart. In these the appendages may protrude 

 more, and the freedom of motion is much greater. The jaws are covered with a 



Fig. 197. 



Fig. 197 



Common Box Tortoise {Terrapene Carolina). 

 Shufeldt. 



Photographed from hfe by Dr. R. W. 



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 hawks-bill turtle 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 completely ossi- 

 fied. The ' ' snappers ' ' are ferocious animals, the big snapper of the Southern states 

 being particularly vicious. 



Order II. Squamata {Lizards). Suborder Sauria. — 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. 



