2ri6 VEItTEBKATE ANIMALS. 



teeth. The tyj)ic;il Frogs have enormously developed hind-legs, the 

 toes of which are united by membrane, or aie " webbed." They 

 swim very powerfully, and can take extensive leaps. Excellent ex- 

 amples are the Grass Frog {Rana tcmporaria) and Edible Fi-og 

 (liana esculenta) of Europe, and the Bull -frog {Rana pipiens) of 

 North America. The Tree-fiogs, on the other hand, are adapted 

 for a wholly different life, inhabiting trees, among which they climb 

 with great ease by the help of suckers developed upon the ends of 

 the toes. They are mostly found in warm countries, especially in 

 America, but one species is European. 



In the equally familiar Toads {Bufoniche), tlie structure of the 

 tongue is the same as in the Frogs, but the jaws are not furnished 

 with teeth. In the Surinam Toads {Pipidce) there is no tongue at 

 all, and visually no teeth. 



Order IV. Labyrinthodontia. 



Thi,s, the Last order of the Amijidhiu, is not represented by any 

 living forms, arid requires to be little more than mentioned. The 

 Labyrinthodonts were Amphibia which were all of large size, and 

 of which some must have attained absolutely gigantic dimensions, 

 tlie skull of one s[)ecies being three feet in length and two in breadth. 

 They were first known to science simply by their footjn-ints, which 

 were found in certain Secondary sandstones {Trias). These foot- 

 prints consisted of a series of alternately placed pairs of hand-shaped 

 impressions, the hinder print of each pair being much larger than the 

 fore one. So like were these prints to the shape of the human hand 

 that the unknown animal which had jiroduced them was christened 

 the ^^Cheirotheriuni" ((/!r. c/ieii; hand ; (//■;>% beast). Further researches, 

 however, showed that these footprints were produced by various 

 species of large Amphibians, to which the name of Labyrintkodontia 

 was apjilied, in consequence of the complicated microscopic structure 

 of the teeth. These extinct Amphibians are known to have exi.sted 

 at the time of the C^oal, but they are most characteristic of the period 

 known to geologists as the Trias, 



