178 



AMPHIBIA. 



usually small teeth, and the lower jaw sometimes. The hind- 

 limbs usually have the digits webbed for swimming, and are 

 generally much larger and longer than the fore-limbs. 



Fig. 539. — Skeletou of the common Frog (Rana temporaria). d. Dorsal vertebrae, 

 ■with long transverse processes. 



The Reolocjical history of the Anoura, as in the case of the 

 TJrodela, is of small importance. The two chief groups of 

 the li^dng Anoura — namely, the Frogs and the Toads — are 

 both represented in past time ; but they do not appear to 

 have come into existence till after the commencement of the 

 Tertiary period. ^lost of the fossH forms have been detected 

 in deposits of Miocene age. 



Order IV. Labyrixthodoxtl\. — The members of this, the 

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

 Batrachians, probably most nearly allied to the Urodela, but 

 mostly of large size, and some of gigantic dimensions, the 

 skull of one species {Lahyrinthodon Jcegeri) being upwards of 

 three feet in length and two feet in breadth. The Laby- 

 rinthodonts were first known to science simply by their foot- 

 prints, 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 



