240 



ZOOLOGY 



SECT. 



large green edible Frog found on the continent of Europe and 

 occasionally in England. Other species of the same genus occur 

 in all parts of the world except New Zealand, the southern part of 

 South America, and the various oceanic islands. 



External Characters.- -The trunk is short and stout, and is 

 continued, without the intermediation of a neck, into the broad, 

 depressed head. There is no trace of a tail, the anus being terminal. 

 The mouth also is terminal, and is characterised by its extra- 

 ordinary width, the gape extending considerably behind the eye. 

 On the dorsal surface of the snout are the small nostrils ; the eyes 

 are large and prominent, and each is provided with an upper eyelid 

 in the form of a thick fold of skin and a nictitating membrane, a 



FIG. SGI'. Rana temporaria. (From Mivart.) 



much thinner fold, which arises from the lower margin of the eye 

 and can be drawn up over it. Close behind the eye is a circular 

 area of tensely-stretched skin, the tympanic membrane, a structure 

 not met with in any Fish : as we shall see, it is an accessory 

 auditory organ. There is no trace of branchial apertures. 



The back has a peculiar bend or hump, in the sitting posture, 

 marking the position of the sacral vertebra. The limbs are of 

 very unequal size. The fore-limits are short, and each consists of 

 an upper arm. which, in the ordinary position, is directed back- 

 wards and downwards from the shoulder-joint ; a fore-arm, directed 

 downwards and forwards from the elbow ; and a hand, ending in 

 four short tapering digits, directed forwards. The hind-liml) is of 

 great size ; in the usual squatting posture the thigh is directed 



