ORDERS OF AMPHIBIA. 417 



example of this family. The Natter-jack Toad is the only 

 other British species, but about fifty other forms are known, of 

 which many are American. 



In the RanidcB the tongue has the same form as in the 

 Toads, but the upper jaw always carries teeth. The hind- 

 limbs, are much larger than the fore-limbs, and are fitted for 

 leaping, whilst the toes are webbed. The toes of the fore- 

 limbs are free. The common Frog (Rana temporaria) is a 

 good example of the typical Ranida. Larger than the common 

 Frog is the Eatable Frog {Rana esculentd) of Europe, and larger 

 again than this is the Bull-frog (Rana fipiens) of North Amer- 

 ica. The Tree-frogs (Hyld) are adapted for a wholly different 

 mode of life, having the toes of all the feet furnished with ter- 

 minal suckers, by the help of which they climb with ease. 

 They are mostly found in warm countries, especially in Ame- 

 rica, but one species (Hyla arborea) is European (fig. 1 54). 



Order IV. Labyrinthodontia. — The members of this, 

 the last order of the Amphibia, are entirely extinct. They 

 were Batrachians, probably most nearly allied to the Urodela, 

 but all of large size, and some of gigantic dimensions, the skull 

 of one species {Labyrinthodon Jdgaeri) being upwards of three 

 feet in length and two feet in breadth. The Labyrinthodonts 

 were first known to science simply by their footprints, which 

 were found in certain sandstones of the age of the Trias. 

 These footprints consisted of a series of alternate pairs of 

 hand-shaped impressions, the hinder print of each pair being 

 much larger than the one in front (fig. 161). So like were 

 these impressions to the shape of the human hand that the 

 unknown animal which produced them was at once christened 

 Cheirotherium, or " Hand-beast." Further discoveries, however, 

 soon showed that the footprints of Cheirotherium had been 

 produced by different species of Batrachians, to which the 

 name of Labyrinthodonts was applied, in consequence of the 

 complex microscopic structure of the teeth. 



Fig. 161. — Footprints of a Labyrinthodont iCheiroiherhim). 



The labyrinthodonts were " salamandriform, with relatively 

 weak limbs and a long tail."- — (Huxley.) The vertebral centra ' 

 and arches were ossified, and the bodies of the dorsal vertebrae 



