236 BRANCH CHORDATA 



the evening, feeding on insects. Gadovv mentions a tree-frog which lived 

 twenty-one years. 



Family Ran'idae. — Frogs {RuniiKi:} have teeth in the upper jaw. The 

 toes, four to five, arc more or less \vcl)l)cd. The tongue is like the toad's. 



Our largest species is the bullfrog (Ra'na catesbia'na) , which measures 

 from 5 to 8 inches. It is known by its deep bass voice. It has two 

 large internal vocal sacs. Its toes are broadly webbed. In color it is 

 varying shades of green above, with faint dark spots, the head is bright 

 green, the legs blotched. The tympanum is large. Its hind limbs are 

 much prized for food. Bullfrogs are solitary except in the breeding season, 

 when hundreds collect in the same small pond. They are commonly found 

 sitting half immersed in water, or waiting for their prey upon the banks 

 of a pond. The bullfrog is voracious, devouring mollusks, fishes, and frogs, 

 as well as ducklings and young water fowls. It is eaten by fishes, birds, 

 otters, snakes, and alligators. 



The green frog {R. clamafa) is a brownish-green color, brighter in front, 

 with irregular small black spots, and blotched limbs. Below, the color is 

 yellowish white. The tympanum is large. It is common in the eastern 

 United States. The vocal sacs are small and internal. 



Wallace describes a species of Raniiln' which was brought to him in 

 Borneo. The body was about 4 inches in length and the webs of both fore 

 and hind feet were enlarged and used as parachutes by these " flying frogs" 

 (Fig. 195). 



Classification. — 



Order. Examples. 



I. Stegoceph'al'ia. Extinct forms. 



II. Ap'oda or Gymnophi'ona. Coeciliidse. 



III. Urode'la or Cauda'ta. Necturus, Salamanders. 



IV. Anu'ra or Ecauda'ta. Frogs, Toads. 



CLASS IV. REPTILIA 



This class of Chordates consists of snakes, lizards, turtles, 

 crocodiles, and alligators, together with a number of extinct 

 orders. "Compared with the ages that are gone the reptile life 

 upon our globe has decreased to mere parasitic proportions." — 

 Ditmars. 



Reptiles are scaly. They are aquatic or terrestrial; a few 

 are arboreal. There is one occipital condyle, and the lower jaw 

 is united to the base of the skull by a quadrate bone. 



The limbs are four, two (the Python and some kindred forms 

 have the vestiges of the hind limbs only), or none, as in the 

 "glass snake" and our common snakes. 



Reptiles are poikilothermal. The heart has one ventricle 

 and two auricles, except in order Cro'codilia, where the heart has 

 two auricles and two ventricles. 



