AMPHIBIA. 285 



limbs lacking ; Siren, the mud eel of southern United States, has 

 jaws armed with horny sheaths. PROTEID^E, hind limbs present ; 

 jaws with teeth. Proteus of Austrian caves nearly blind ; 

 Necturus (Menobranchus), the mud puppy of the central United 

 States. 



ORDER II. DEROTREMATA (CRYPTOBRANCHIA). 



External gills lost, a spiracle on the side of the neck, lead- 

 ing to persistent gill slits. AMPHIUMIDYE, limbs rudimentary ; 

 AmpJiiuma, one species, the congo eel from the southern states. 

 CRYPTOBRANCHID^E, legs strong ; body salamander-like. Men- 

 opoma (jCryptobranchns), hell-bender, from U. S. Megalobatra- 

 chus, giant salamander from Japan, three feet long. Andrias 

 scheuchzeri, European miocene, described over one hundred and 

 fifty years ago as a relic of the legendary Noachian deluge. 



ORDER III. SALAMANDRINA (MYCTODERA). 



Gill slits and external gills lost in the adult ; vertebrae fully 

 ossified. LECHRIODONTA, palatine teeth in a transverse row or 

 posteriorly converging series. Amblystoma, toothless parasphen- 

 ' oid, toes four in front, five behind ; many species in U. S. 

 PletJwdon, teeth on parasphenoid ; premaxillaries separate. 

 Spelerpes, premaxillaries fused ; Desmognathus, with parasphen- 



FIG. 283. Plethodon erythronotus. 



oid teeth and opisthoccele vertebras. The species of Amblys- 

 toma are remarkable for the length of time that their larvae 

 (Siredon) retain their gills, some species (A. tigrinutri) and the 

 axolotl of Mexico breeding in the siredon stage. Most of the 

 lungless salamanders (p. 27) belong in this family. MECOD- 

 ONTA, parasphenoid toothless, palatine teeth in two rows diver- 

 ging behind. Diemyctylus, our common newt. In Europe Triton, 



