54 CADUCIBRANCHIATA. 



a metamorphosis in their case exceedingly probable un- 

 der favorable conditions. In naming them here the ge- 

 neric term, Siredon, though perhaps inappropriate, is re- 

 tained where a better has not been given, because when 

 the adult is discovered, it will probably be some already 

 well known Salamander, and in the present state of sci- 

 ence to assign them new designations would only add 

 to the already burdensome list of synonyms. Also the 

 characteristics of Siredon are. still valuable as referring 

 to the young, and hence are given as follows. 



Siredon, Wagler. 



axolotl, rarely atolocalt. 



Body short and thick; head depressed; tongue small; 

 vomerine teeth numerous, small, disposed obliquely to 

 the palatine and pterygoid bones ; trunk short, slightly 

 compressed; external branchial tufts three, partially 

 covered at base by a floating skin ; gular folds repre- 

 senting the operculum; feet four, well developed; toes 

 free, four in front, five behind; tail compressed, not sep- 

 arable from the body. 



