CLASS REPTILIA 



429 



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Figure 304. Ichthyosaurus, a. fishlike reptile, and young. This fossil reptile had a fish-shaped 

 body, porpoiselike snout, short neck, and dorsal and caudal fins. The limbs were modified into 

 paddles, a remarkable adaptation for swimming. (Courtesy of American Museum of Natural 

 History.) 



their digits are usually provided with claws; the 

 majorits- of them possess functional legs; and 

 they breathe by lungs. 



Bogert estimates that there are about 7000 

 or more species of living reptiles which may be 

 grouped into 4 orders: (1) the Chelonia (Tes- 

 tudinata), containing about 275 species of 

 turtles, terrapins, and tortoises; (2) the Rhyn- 

 chocephalia, represented by a single New Zea- 

 land species; (3) The Squamata, containing 

 about 6700 species of lizards and snakes; and 

 (4) the Crocodilia, containing 25 species of 

 crocodiles, gavials, alligators, and caimans. 



Order 1. Chelonia ( Testudinata ) . Turtles, 

 terrapins, and tortoises. Body en- 

 cased in bony capsule; jaws with- 

 out teeth. 

 Family 1. Chelydridae. Snapping tur- 

 tles (Fig. 278). Exs. Chely- 



dra serpentina, snapping tur- 

 tle, and musk turtles, 

 Kinosternon. 



Family 2. Testudinidae. Tortoises and 

 most turtles. Ex. Chrysemys 

 picta, painted turtle (Fig. 

 278). 



Family 3. Cheloniidae. Sea turtles. Ex. 

 Chelonia mvdas, green turtle 

 (Fig. 282).' 



Family 4. Dermochelidae. Leatherback 

 turtle. Ex. Dermochelys 

 coriacea, leatherback turtle 

 (Fig. 274). 



Family 5. Trionychidae. Soft-shelled 



turtles. Ex. Amyda spinijera, 



soft-shelled turtle (Fig. 



280). 



Order 2. Rhynchocephalia. One genus of 



New Zealand lizardlike reptiles. 



