CHORDATA 





tion. They are found almost exclusively in the northern hemi- 

 sphere. In some the gills persist throughout life, and they are 

 naturally aquatic in habit. This is true of the genus Siren ( Fig. 

 310), the mud eel of our Southern states, and also of Necturus 



ircl.i br.cl.2 

 FlG. 311. Necturus maculatus 



an, anus; br.r-br.j, externa) gills; br.J.iw\ 

 (After Parker and Haswell.) 



(Fig. 311), the mud puppy of our Central states. In some the 

 external gills have disappeared, but the gill slits persist and com- 

 municate with the outside by a cleftlike opening in the neck 

 region. Examples of this condition are found in the Congo 

 eel, Amphiuma (Fig. 312), of our Southern states, and the hell- 

 bender, or water dog, Protonopsis horrida, of the Ohio river, 

 alamander-like in appearance, and said to be excellent as food. 

 The latter ranges from thirty to sixty centimeters in length and 

 is entirely harmless. Closely related to these two is the giant 



FlG. 312. Amphiuma tndactyla. (From Parker and Haswell's Text-book.) 



salamander of Japan and Thibet, Megalobatrachns maxtmus, 

 which attains a length of nearly a meter; it is the largest living 

 amphibian. 



Finally there are the true salamanders in which neither ex- 

 ternal gills nor gill slits are present in the adult. Some are con- 

 fined to Europe, as the yellow-spotted salamander, Salamandra 

 maculosa, and the smaller, black Salamandra atra, which are 

 noteworthy because they are viviparous, a very exceptional con- 

 dition in the Amphibia. Our common newt belongs to the genus 

 Diemyctylus, which is widely distributed over the whole norther 



