DOLPHINS AND SIRENS. 47 



The chief peculiarity of this animal is the elongated 

 head, and especially the manner in which the lower 

 jaw is prolonged beyond the upper. Like the Porpoise, 

 it has its teeth interlocking with each other so per- 

 fectly, that when the jaws are closed, the blade of a 

 penknife can scarcely be passed between the teeth ; 

 sharp, and slightly curved backwards. As there are 

 nearly two hundred teeth in the jaws, the whole appa- 

 ratus forms a trap from which scarcely any fish is 

 likely to escape. 



On looking at these jaws, we may well ask our- 

 selves the reason why they differ so much in shape 

 from those of the Porpoise, although they are evidently 

 intended for the same object. The reason is evident 

 when we inquire into the manner in which it 

 feeds. 



Like the Porpoise, it is fond of pursuing shoals of 

 fish whenever it can find them. But its principal 

 food consists of various flat fish. These creatures, as 

 all know who have visited any large aquarium, gene- 

 rally lie flat on the sand, with their heads a little 

 raised above it, and their bodies often covered with a 

 thin layer of sand which has been raised while the 

 fish is settling down. The rounded jaws of the Por- 

 poise would find great difficulty in capturing one of 

 these fish ; but the Dolphin, when it sees a sole, a 

 plaice, or similar fish lying on its sandy bed, shoots 

 rapidly towards it, drives its long under-jaw beneath 

 it, and so scoops it up before it has time to escape. 

 It is remarkable that some of the diving birds use 

 their beaks in exactly the same manner. 



One of the strangest of these animals is the Narwhal, 



