1 58 ZOOLOGY. 



need not here be enumerated, which characterize the 

 important class, Amphibia. (See chap, xii., 10.) Again, 

 among common Amphibia we can easily recognize two 

 clearly separated orders the TJrodela, represented by the 

 newt and salamander, which retain a long tail and have 

 numerous vertebrae and small limbs ; and the Aimra, 

 including frogs and toads, which lose their tail, have few 

 vertebras, and powerful limbs. Two other orders, one 

 confined to tropical regions, the other entirely extinct and 

 known only as fossils in Carboniferous and Permian strata, 

 need only be mentioned here. 



Among Aiiura we can distinguish two sub- orders one 

 represented by the toad, in which (among other things) 

 the ventral ends of the coracoids do not meet in a syinphysis 

 but end freely and overlap (Arcifera) ; the other, to which 

 the frog belongs (Firmisternia). In most respects, how- 

 ever, a toad will show practically the same characters as a 

 frog, in dissection. Finer distinctions mark off the family 

 Ranidve from other families of the Firmisternia, such as 

 the Hylidse (tree frogs), and still finer ones, the genus 

 Rana from other genera of the family. 



