THE SHARK'S TEETH 



tion, but in contrast to it we must also note complica- 

 tions and superpositions which denote, in her general 

 action of creating life, a variety and superiority of 

 methods far greater than we could possibly imagine. 



The strong triangular teeth of the porbeagle, which 

 we also find in other members of the family, such as 

 the blue shark, are only one type of this dental outfit. 

 There are many others, and their diversity is surprising. 

 Sometimes, the teeth differ in form in the two jaws: 

 one set being conical, and the other flat, with a cutting 

 and notched edge. In certain fish, like the smooth 

 hound, a kind of dogfish, these teeth, instead of 

 pointing upward, turn downward, and lie in plates 

 set side by side, like paving stones. Certain species 

 of skate, which are related to the sharks and in which 

 similar facts can be observed, show an arrangement 

 varying according to sex or age. And finally, certain 

 sharks, now only found as fossils, which peopled the 

 seas of the late Palaeozoic era, had teeth in their jaws 

 which had crests, corrugated, twisted, spiral, looking 

 almost like the folds and convolutions which were 

 found in several large reptiles of the Mesozoic era, 

 and are still to be seen in the ruminants on land to-day. 



If we go outside the group of sharks and skate, 

 we find in other fishes similar dispositions, which go to 

 prove the same absence of a relation between organ 

 and function. Some predatory species capable of 

 attaining a great speed, like the tunnies, have small, 

 short teeth, while other species of a more sedentary 

 type are better supplied, although they do not seem to 

 have the same need. In fresh water, two different 

 fishes, the trout and the bleak, have much the same 

 mode of life and the same prey, but while the former 

 has teeth, the latter has toothless gums, or pharyngeal 

 teeth only at the back of its mouth, at the entrance to 

 the pharynx, and these afford no aid in snapping up 

 the victim in deep water. The bright-hued wrasse 

 has two sets of teeth, one on the jaws and one in the 

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