INTRODUCTION. TO THE CLASS OF REPTILES 7 



The majority of reptiles are covered with scales, or armor 

 of solid bone, and are provided either with teeth for conflict 

 and offence, or with armor for defence. Their means of loco- 

 motion show a wide range of variation, beginning with the 

 clumsy-flippered harp turtle, passing the gila monster, the 

 swift-footed monitor, the kangaroo-like collared lizard (of 

 Arizona), the gliding serpents, and ending with the flying 

 dragon. 



In their food habits the range of the world's reptiles is 

 infinitely great, embracing fruit, vegetables, herbage and all 

 forms of flesh, living and dead. Oddly enough, however, no 

 modern reptile has been provided with molar teeth for the 

 mastication of food. The saurians, lizards and serpents have 

 teeth for seizing and holding their living prey. The turtles, 

 however, are quite toothless, and in place of teeth their horny 

 jaws have sharp, cutting edges for clipping up their food 

 into pieces small enough to be swallowed without mastication. 



The teeth of serpents and crocodilians generally are per- 

 petually renewed, as fast as old teeth are worn out and 

 disappear. By reason of this the lives of these reptiles are 

 indefinitely prolonged. 



The great majority of reptiles reproduce by laying eggs, 

 which are hatched either by the heat of the sun or by the 

 fermentation of muck-heaps. Many species of serpents hatch 

 their eggs in their own bodies, and bring forth their young 

 alive. Such species are called vivip'arous. Those which lay 

 eggs are called o'viparous. 



Some reptiles, notably the crocodiles and tortoises, con- 

 tinue to grow almost as long as they live. Doubtless this is 



