304 



SYSTEMATIC ZOOLOGY 



hemisphere. The genus Amblystoma is interesting because in 

 some species its larva, known technically as siredon, remains for 

 a long time in the larval condition, with external gills, and even 

 becomes sexually mature in that stage. Amblystoma maculatum 

 is known commonly as axolotl by the Mexicans and is eaten by 

 them. 



SUBCLASS II. ANURA 



The Anura (Gr. a, without, and oupd, tail) consist of the frogs 

 and toads, and are tailless in the adult condition. They are 

 sometimes known as Batrachia (Gr. ftarpdxios, froglike), and this 

 term is sometimes applied to the whole group of Amphibia as 

 well. They are widely distributed over the whole world. The 

 respiration is by lungs in the adult ; the internal nares are at the 

 anterior end of the mouth, and the air passing into the mouth 

 cavity is forced into the lungs by a swallowing movement ; the 



larvae, as in all 

 other Amphibia, 

 are provided with 

 gills. 



A few species 

 aretongueless; of 

 these the best 

 known is a toad, 

 Pipa amcricana 

 (Fig. 313), found, 

 so far as we know, 

 only in South 

 America. Its 

 method of caring 

 for its developing 

 eggs is pretty 

 generally known. The male places the eggs on the dorsal sur- 

 face of the female, and after they are fertilized, the skin grows 

 up around each egg, forming a chamber for it ; over this cham- 

 ber a lid, or operculum, develops, and within the cell thus formed 

 the egg develops into a young toad ; after it leaves the cell, the 

 skin of the female resumes its former normal condition. 



All other toads have tongues ; in some, as in the family Bu- 





Fig. 313. Pipa americana, 5 , the Surinam toad. (From Parker 

 and Haswell's Text-book.) 



