284 PRACTICAL ZOOLOGY 



roundings or to lure other fish within reach of the sharp teeth. 

 When these fish are drawn up to the surface, the gas in the air 

 bladder, being relieved of most of its pressure, expands and often 

 forces part of the alimentary canal out of the mouth. 



Subclass 4. Dipnoi 



The third subclass of fishes contains the Dipnoi or lungfishes 

 (Fig. 167). There are only five species of these alive at the 

 present time. One occurs in Australia, three in Central Africa, 



Fig. 167. — Photograph of a living African lungfish. (Photo, provided by 

 American Museum of Natural History.) 



and one in South America. All of them are able to live in 

 marshes, swamps, and other bodies of stagnant water because 

 their air bladders function as a lung. They are therefore not 

 dependent upon fresh water, but can breathe air. 



REFERENCES 

 See end of Chapter XXIX. 



