226 



Shark and Company 



teeth are on a kind of somatic escalator, with the developing teeth re- 

 posing in the jaw until they are needed. 



The ability of these escalators to continually bring forward identical 

 teeth has been curiously demonstrated in the examination of abnormal 

 teeth found in some captured sharks. In one shark, for instance, an oddly 

 split tooth was found to be duplicated by all the teeth on its escalator 

 track. Each one of them, including the reserve teeth covered by gum 

 tissue, was split down the middle, exactly as the first-row tooth was. Fur- 

 ther investigation showed that a Sting ray's stinger had become im- 



As teeth are lost or worn out, new ones rise up, escalator-like, from the shark's jaws, 

 as this cross-section drawing shows. The dotted lines represent the cartilage. "Budding" 

 teeth are protected by a membrane. After Ridewood 



bedded in the shark's jaw, evidently while the shark digested the Sting 

 ray. The stinger apparently had pierced a tooth bud deep in the jaw, 

 dividing the bud into approximately equal halves. As each succeeding 

 tooth (or, more correctly, half-tooth) moved forward, it carried this de- 

 formity with it. 



In some of the larger sharks, such as the Tiger shark (Galeocerdo 

 cuvieri), the flashing teeth are backed by a huge, powerful jaw. The 

 skull of a horse was found in one Tiger not quite 1 1 feet long. The Tiger 

 was able to swallow, whole, the horse's skull because of the peculiar con- 

 struction of the Tiger's jaws and the muscles that power it. The upper 

 and lower jaws have joints at each comer of the mouth. The joint is 

 manipulated by strong, elastic muscles that enable the shark to distend 

 its mouth. Each jaw, upper and lower, is hinged in the center, so that the 

 lower jaw can gape into a deep V and the upper jaw can erect into a A. 

 With this mechanism, the jaws of a large shark could easily pass over 

 the length of a man without touching him, even if he were somewhat 

 portly, and had, say, a 40-inch waisthne. If those jaws should close, the 

 shark biting and shaking its head, the man could be bitten in half. It 

 has happened. . . . 



