174 BATRACIIIA- 



Class F. BATRACHIA. (The Batrachians.) 



Cold-blooded vertebrates, intermediate between tlie fishes and the 

 reptiles. 'I'hey dilTer from the fishes ehielly in the absence of rayed 

 fins, the limbs being usually developed and functional witli the 

 skeletal elements of the limbs of reptiles, and in the reduction or 

 absence of the various bones of the branchial, opercular and sus- 

 pensory systems. 



Tlie Hatrachians undergo a more or less complete metamorphosis ; 

 the young (" tadpoles ") being fish-like and more or less ai^uatic, 

 breathing by means of external gills. These dilTer from the gilla 

 of fishes in standing on (lesliy processes of the branchial bones and 

 not on the bones themselves. In the tadpole, the tail is provided 

 witli a more or less <lisliiict fin-like menii)raiie, which usually dis- 

 appears with age. Later in life, lungs are devclojird, and in most 

 cases the gills disa[)pcar. Skin mostly naked and moist, used to 

 some extent as an organ of respiration. Heart with two auricles 

 and a single ventricle. 



Reproduction by means of eggs which are of comparatively 

 small size, without hard shell. These are deposited in water or in 

 damp places. In one salamander the young are born alive. Pro- 

 fessor Cope recognizes nine orders of Batrachians, four of these 

 being extinct, {(idrpaxos, frog.) 



Orders of Batrachia. 



a. Body lenpthcncd, with a distinct tail throughout life; hind limbs, if present, 

 not espei-ially fiilarfjcd. 

 6. Extcrnnl frills and K'H-cle^'" persistent throughout life, the pill« 3 on 

 ent-h side; no ej-elids; vertebrae auiphicadian ; maxillary »nmll or 

 wanting. 

 C. Body eel-shaped, without hind legs; teeth on vomer; floor of mouth 

 rough; jaws with horny sheath. . . . Thachvstomata, XXIV. 

 cc. Body siilamander-shaped, the hind limbs present; jaws with teeth. 



I'ltoTKIOA, XXV. 



66. External gills normally disappearing in adult life; limbs 4 (or want- 

 ing, present in all our sjHH-ies); jaws with teeth; maxillarieo and 



palatines present I'kodki.a, XXVI. 



aa. Iknly short, depressed; tail disappearing with age; limbs 4, the po-to'-'or 

 much enlarged SAMi iH Ti A , .\XVII. 



