GENERAL FACTS ABOUT SEA FISH 21 



The teeth of fishes, which might, had the present volume 

 other aims, offer material for a very interesting study in 

 development, must be very briefly dismissed. They differ 

 considerably in bony and cartilaginous fishes. There is, in the 

 former group, distinct anchylosis, but it may not always be 

 easy to determine by casual examination where the tooth leaves 

 off and where the jawbone begins. The teeth also show much 

 variety in the various families, and reference will be made in 

 later chapters to the more or less successful endeavours to 

 associate these types of fish-teeth with different kinds of food 

 or different manners of feeding. In the sea-breams (Pagrus), 

 for instance, the teeth are blunt and round ; in the wolMsh 

 (^narrkicas). there are pointed teeth in front, for seizing living 

 prey, and flatter teeth behind, for crushing shells. Some of 

 our common fishes, such as the pipe-fish (Sygnaihus) and sea- 

 horse (Hippocampus) have no teeth whatever ; in others, such 

 as the grey mullet {Mugil), they are exceedingly feeble ; and in 

 a few, like the red mullet {pvlullus), there are teeth in the lower 

 jaw only. Some fishes, such as the launce {Ammodytes) and 

 globe-fish {^etrodon), have no detachable teeth, but bony or 

 horny continuations of the jaw. The teeth of bony fishes may 

 cover not only the edges of the jaws, but also the tongue and 

 palate ; and in the sun-fish {Orthagoriscus) there is a powerful 

 series of pointed gill-teeth. In sharks and rays {Selachii) the 

 teeth are, as already indicated, really identical with the granula- 

 tions on the skin, and they are moreover not connected with 

 the jaws, as in bony fishes, by ossification, but merely lie 

 embedded in the gums. Even in sharks, however, there are 

 many types of teeth, those of the porbeagle {Lamna), for 

 instance, having smooth, keen edges, while those of the blue 

 shark {Carcharias) are slightly serrated and also differ in the two 

 jaws. In the eagle-ray {0\/[ylioiatis) and some other allied 

 forms the teeth are closely packed in the form of a pavement. 

 In sharks the teeth lie in several parallel rows, one ready to 

 replace the other ; but in rays those on the edge of the jaw are 



