22 THE COMMON FROG. [chap. 



found in England as well as on the Continent of 

 Europe. It is as widely distributed over the Old 

 World as is 7^. temporaria, but it is unknown in 

 America. It is easily to be discriminated from the 

 common species by the absence of that dark, sub- 

 triangular patch which extends backwards from the 

 eye in R. teniporaria. 



Fig. 4.— The Edible Frog {Rana escHlenta\ 



The male of R. esciilenta is further to be distin- 

 guished from the male of the common Frog by the 

 fact of its having the floor of the mouth, on each side, 

 distensible as a pouch — the pouches, when distended, 

 standing out on each side of the head. These pouches 

 are called ''vocal sacs," and no doubt aid in inten- 

 sifying these animals' croak, which is so powerful 

 that (on account of it and because of the country 

 where they are common) they have been nick- 

 named ''Cambridgeshire Nightingales." Specimens 



