304 ELEMENTARY ZOOLOGY. 



The three principal families are the frogs, the toads, and 

 the tree-toads. They include 80 per cent., or more, of 

 the species of amphibians. One of the largest is a toad 

 of the Bermudas, which is the only form that develops in 

 partly brackish water. Many of the toads have most 

 remarkable breeding habits, adapting them to their 

 conditions of life. 



312. Key to Some of the Common Amphibians. 



With tail in the adult ; body elongated Order Urodela. 



Gills persistent through life. Perennibranchiata. 



Body eel-like; hind legs wanting, 



Siren, or mud-eel of the South. 

 Body lizard-like; hind limbs present, 



Necturus; mud-puppies. 



Gills lost, but slit remaining Derotremata. 



Limbs rudimentary. .Congo snake of the Southern States. 

 Limbs well developed .... Cryptobranchus, the hell-bender. 



All traces of gills lost Mictodera. 



Six to 8 inches long ; black with yellow spots, 



Amblystoma, salamanders. 

 Three to 4 inches long ; olive green or brown, 



Spelerpes, newts. 



With no tail in the adult Order Anura. 



Suited for climbing and living in trees, 



Hyla, etc. (tree-toads). 

 Land forms; more active at twilight, 



Bufo (the commo > toads). 



Land and water Rana (frogs) . 



Body green. 



Large, faintly spotted ; head pale green, 



Rana catesbiana (bull-frog). 

 Small, uniform green, with small dark spots, 



Rana clamitans (green frog). 



Small, with irregular splotches of black, edged with white, 

 Rana halecina (leopard frog). 

 Body not green. 



Bright brown on back; two rows of oblong, dark 



brown splotches on back. Rana palustris (pickerel frog) . 



Pale reddish brown; legs and arms barred with brown, 



Rana sylvatica (wood frog). 



