100 



INTRODUCTION. 



extremely difficult to discern the limit between the 

 two. The term " body " is, therefore, used in the 

 description as meaning both head and body. Its lon- 

 gitudinal measurement is taken to the origin of the 

 hind limbs. The tail consists of a fleshy muscular 

 portion bordered above and below by membranous 

 expansions, termed respectively the upper and lower 

 crest. By depth of the tail is meant its greatest 

 depth, crests included, and the length is measured 

 from the posterior extremity of the body. 



Mouth (Fig. 42). — This term is used in its wider 

 sense, i. e. to include the much-developed lip surround- 

 ing, like a funnel directed downwards, the horny beak, 

 not unlike that of a cuttle-fish, which forms the 

 entrance to the mouth proper. The characters offered 

 by this circular lip are among the most important for 

 the distinction of species. The lip may be entirely 

 bordered by fleshy papillae (l.p.), or these may be re- 

 stricted to the sides, or to 

 the sides and the lower 

 border. Its inner surface 

 is furnished with ridges 

 armed with series of 

 minute bristle-like erect 

 horny teeth (t), each of 

 which, when strongly 

 magnified, is seen to be 

 formed of a column of 

 superposed cones, hol- 

 lowed out at the base 

 , and capping each other 



Horny teeth of Bana acjilis (a) (Fig. 43) ; the Summit 01" 

 and Pelobatesfuscus (b). (After crown f each of these 

 Van Bambeke.) • -, -, , 



cones is expanded, spatu- 

 late, hooked backwards, and usually multicuspid. 

 The denticles are absent in Pelobates and Pelodytes, 

 and present in all the other genera. The number of 

 these columns is very great. F. E. Schulze has 

 counted as many as 1100 in the lip of Pelobates fuscus. 



Fig. 43. 



