Reptilia. 207 



ten or twelve feet. Alligators are confined to the western 

 hemisphere, occurring in the Southern states, Central and 

 South America. 



Crocodiles are found in both the old world and the 

 new. One species is found in southern Florida. 



Extinct Reptiles. In earlier geologic ages reptiles were very much 

 more numerous than at present. Not only were they more abundant, 

 but there were more kinds ; and many of them were large, some being 

 eighty feet in length. Some were lizardlike, with long, slender necks. 

 Others were fishlike. Some had resemblances to birds. The tracks of 

 many of these ancient reptiles in the mud have hardened into rock, and 

 have often been called " fossil bird tracks.' 1 Perhaps the most remark- 

 able were the flying reptiles. They are supposed to have been rather 

 batlike in appearance. The remains of these reptiles are found in rocks 

 in many parts of the world, and the age in which they were most preva- 

 lent is called by geologists the " Age of Reptiles." 



General Characteristics of Reptilia. Reptiles are cold- 

 blooded vertebrates, covered with scales, and when toes 

 are present they end in claws. There is no metamorphosis 

 after leaving the egg. There are no gills at any stage of 

 life. Reptiles produce large eggs which are covered by a 

 tough limy or leathery shell. Some reptiles are ovo- 

 viviparous. Reptiles show a decided advance beyond 

 amphibians in the development of the nervous system ; 

 in the respiratory system, since they breathe by lungs 

 after leaving the egg ; and in the circulatory system, the 

 heart of the alligator having four cavities, as in birds and 

 mammals. 



CLASSIFICATION OF REPTILIA. 



f Lacertilia lizards. 



{Order i. Squamata. j ..... . 



(Ophidia snakes. 

 Order 2. Chelonia turtles. 

 Order 3. Crocodilia alligators. 



