290 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1952 



on land and the larval stage is greatly abbreviated, the eggs giving 

 forth perfect, though very small, frogs. 



REPTILES 



The reptiles were the third class of vertebrates to appear as 

 fossils, in the late Carboniferous. At the present time they are 

 represented by only four groups, rhynchocephalians (Hatteria or 

 Sphenodon, confined to New Zealand) , crocodilians, turtles, and snakes 

 and lizards. Most reptiles are strictly terrestrial with their activities 

 confined wholly to dry land, especially in hot or more or less arid 

 regions, but the crocodilians, many turtles, and some snakes are am- 

 phibious, feeding largely or wholly in water though laying their eggs 

 on land. The sea snakes are wholly aquatic. A few lizards and 

 some snakes frequent the banks of streams or other bodies of water 

 and enter the water freely though they do not feed in it. In warm 

 regions a few blind and legless lizards are subterranean. No 

 reptiles live in the dark recesses of extensive caves. 



The great majority of reptiles are carnivorous, the smaller ones 

 feeding mainly on insects, the larger ones on vertebrates, especially 

 mammals and fish. Some of the snakes have highly specialized 

 feeding habits, as the &gg-, slug-, or snake-eating snakes, and the 

 venomous snakes. The only other vertebrates with a venomous bite 

 comparable to that of the venomous snakes are certain shrews among 

 the mammals. The green turtle, the land tortoises, the large iguanas 

 in tropical America, Madagascar, and Fiji, and a few other lizards 

 are vegetarians ; but the green turtle, up to a length of about 10 inches, 

 is carnivorous. One iguana in the Galapagos Islands feeds on sub- 

 merged seaweeds. Some turtles are more or less omnivorous. 



All reptiles are completely covered with scales or plates. The skin 

 is dry. 



Most reptiles have two pairs of functional limbs adapted to walking, 

 running, swimming, or climbing, but in some the anterior or poste- 

 rior pairs, or both pairs, may be absent. The limbs when present 

 usually end in a group of functional digits which in climbing lizards 

 may be long. In some turtles, particularly the sea turtles, the limbs 

 may be modified as paddles, the forelimbs being much larger than 

 the hind limbs and the chief organs of locomotion, as in the penguins 

 among the birds. Some lizards and snakes, like flying squirrels, 

 Galeopithecus, and a few other mammals, are modified for gliding 

 through the air, but without modification of the limbs. 



The body temperature of reptiles is uncontrolled, approximating 

 that of the surroundings. Some snakes, lizards, and turtles and the 

 American and Chinese alligators hibernate during the winter, most 

 of the turtles and the alligators in water. 



