298 ELEMENTARY ZOOLOGY 



The batrachians which retain external gills in the adult 

 stage are the members of two families of which the 

 American representatives are known as mud-eels (Siren} 

 and mud-puppies or water-dogs (Necturus)* The mud- 

 eels, which are found * * in the ditches in the swamps of 

 the southern States from South Carolina to the Rio Grande 

 of Texas and up the Mississippi as high as Alton, Illinois, ' ' 

 are blackish in color, have no hind legs and are long and 

 slender, with the tail shorter than the rest of the body. 

 They reach a length of nearly three feet. The mud- 

 puppies, found in the Great Lakes and in the rivers of the 

 upper Mississippi valley, are brown with colored spots, 

 and are about two feet long when full grown. They have 

 both fore and hind legs. 



A few salamanders, while not possessing external gills 

 when adult, have a spiracle or small circular opening in 

 the side of the neck which leads into the throat. The 

 best-known American salamander of this kind is the 

 large heavy-bodied blackish water-dog or ' ' hellbender ' ' 

 (Cryptobranchus) of the Ohio River. It is about two feet 

 long, and is <4 a very unprepossessing but harmless 

 creature." It has a conspicuous longitudinal fold of skin 

 along each side of the body. The largest known ba- 

 trachian, the giant salamander of Japan (Megalobatrachus\ 

 reaching a length of three feet, is related to the water- 

 dog. 



Of all the salamanders the most interesting are the 

 blunt-nosed salamanders (Amblystoma}. A dozen or 

 more species of A mblystoma occur in North America, of 

 which tigrimim, a dark-brown species with many irregular 

 yellow blotches sometimes arranged in cross-bands, is the 

 most widespread. The larvae of some Amblystoma retain 

 their gills until they have reached a large size, and in one 

 or two species the usual metamorphosis is very long 

 delayed and the salamanders produce young while in the 



