250 



PISCES 



heavy whaleboat. The swordfish is one of the finest of the food- 

 fishes, but utilized in New England chiefly. The sailfish is another 

 odd type. 



The cod, the haddock, and the hake are all important members of 

 the family Gadidae. The cod is now especially valuable as a source 

 of cod liver oil. This oil has been used as a remedy for growth 

 deficiencies for many years, but recently its importance has been 

 much emphasized by the " vitamin " enthusiasts. (Figure 135.) 



Fig. 132. Shark suckers. (Courtesy of Amer. Mus. of Nat. Hist.) 



Subclass Dipnoi. (Gr., " two breathing apertures.") — The Imig 

 fishes have a heart with the beginnings of a division into two auricles. 

 Gill respiration is combined with the use of a modified swim bladder 

 which acts as a lung. A posterior naris opens into the mouth cavity. 

 They have paired fins and persistent notochord. The Australian 

 lung-fish ( Neoceratodus fosteri) feeds on worms, crustaceans and 

 mollusks secured from the bottom vegetation. Its single lung is 

 utilized when it comes to the surface. It can survive in stagnant 

 and polluted water where other fishes perish. (Figure 137.) 



