TEETH OF THE SHARK. 339 



alone the structure and the instincts could be 

 adapted to each other. 



Specimens of almost every species of the shark 

 family Squalidce have been found on the British 

 coasts, but the largest and most formidable of the 

 tribe are rare. Most visitors of our sea-shores, 

 however, must be familiar with one or other of the 

 minor species of shark, called dog-fish, of which 

 there are several kinds, and which frequent some 

 parts of our coasts in immense multitudes, occasion- 

 ing great havoc among the nets and fishing lines, 

 and often tearing to pieces the best fish on the 

 hooks. A very remarkable example of beneficent 

 care has been* observed in relation to the teeth of 

 the shark. In the larger specimens the teeth, 

 from their extraordinary and indiscriminate vora- 

 city, must be exposed to frequent injury, and 

 without some provision by which those terrible 

 weapons of destruction may be renewed the shark 

 tribe would have become extinct, or their peculiar 

 functions, that of thinning the number of the inha- 

 bitants of the deep, would be rendered impossible. 

 Accordingly the teeth of shark are not fixed in 

 sockets, but attached to a cartilaginous membrane. 

 This membrane grows outward ; the outer row of 

 teeth in due time drop out, and another row 

 which has been gradually advancing occupies the 

 place of the first ; this in due time disappears and 

 other sets follow in succession. By this means, 

 even in the oldest of these monsters of the deep, 

 the teeth are always in the most perfect condition 

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