AMPHIBIANS. 341 



fossils, grouped under the name STEGOCEPHALI, some of 

 which had skulls five feet or more in length. 



ORDER III. ANURA (Frogs and Toads). 



These, in the adult condition lack a tail, and have appen- 

 dages fitted for leaping. The lower jaw is without teeth. 

 The larvae are always tailed, and have at first external 

 gills. Frogs (Ranidse) and toads (Bufonidae) differ in that 

 frogs have a smooth skin, and teeth in the upper jaw; 

 toads have a warty skin (caused by numerous glands) and 

 no teeth. Tree-toads (Hylidse) are more frog-like, but 

 they have sucking discs on the ends of the toes, by means 

 of which they are adapted to a life in trees. Another 

 group (Aglossa) occurs in the tropics, in which the tongue 

 is absent. 



Some of the Anura have strange breeding habits. Thus 

 in the European Alytes the male wraps the long string of 

 eggs about his body and carries them there until they 

 hatch. In Nototrema of South America the skin of the 

 back forms a pouch, in which the eggs are carried; while 

 in the Surinam toad (Pipa) the skin of the back becomes 

 very much thickened, leaving little cups, in each of w r hich 

 an egg is placed, and here the young are hatched out. 



Another interesting form is the flying tree-toad of the 

 East Indies, in which the feet with the web between the 

 toes become greatly enlarged, forming large discs, upon 

 which the animal sails, much as does a flying squirrel upon 

 its lateral folds of skin. 



