CHAPTER XIX 

 SUBPHYLUM VERTEBRATA: CLASS V. REPTILIA 



The reptiles constitute one of the most interesting, but gener- 

 ally least known, classes of the Vertebrata. They are cold- 

 blooded; usually covered with scales and frequently with bony 

 plates; and breathe with lungs. The popular notion that reptiles 

 are slimy is erroneous. Contrary also to general belief, very few 

 reptiles, at least in the United States, are dangerous to man, but 

 the majority of them are harmless and many even beneficial. 

 The reptiles that are living to-day are but a remnant of vast 

 hordes that inhabited the earth's surface in prehistoric times. 

 In fact, of the twenty orders of reptiles now recognized by her- 

 petologists, only four possess living representatives, and one 

 of these includes only one nearly exterminated species con- 

 fined to New Zealand. The four orders of living reptiles are as 

 follows : — 



Order i. Testudinata (Chelonia). — Turtles and Tor- 

 toises. 



Order 2. Rhynchocephalia. — One lizard-like reptile con- 

 fined to New Zealand. 



Order 3. Crocodilini. — Crocodiles, Alligators, Ga vials, and 

 Caimans. 



Order 4. Squamaia. — Chameleons, Lizards, and Snakes. 



1. The Turtle 



The turtle has been selected as a type of the Reptilia. It 

 will not be discussed in detail, as was the frog, but only the more 

 important points regarding its external and internal anatomy 

 and physiology will be mentioned. 



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