JAWS OF FISHES. 127 



horny jaws, having a remarkable resemblance 

 to the bill of a parrot ; excepting that the lower 

 piece is the largest of the two, and covers the 

 upper one, which is the reverse of what takes 

 place in the parrot. These constitute a powerful 

 instrument for breaking the shells of the mol- 

 lusca and Crustacea which compose the usual 

 prey of these animals. 



Fishes almost always swallow their food entire, 

 so that their jaws and teeth are employed prin- 

 cipally as organs of prehension and detention ; 

 and the upper jaw, as well as the lower one, 

 being moveable upon the cranium, they are 

 capable of opening to a great width. The bony 

 pieces which compose the jaws are more nume- 

 rous than the corresponding bones in the higher 

 classes of vertebrata, and they appear, therefore, 

 as if their developement had not proceeded suf- 

 ficiently far to effect their consolidation into 

 more compact structures.* 



Fishes which live upon other animals of the 

 same class having a soft texture, are furnished 

 with teeth constructed merely for seizing their 

 prey, and perhaps also for slightly dividing it, 

 so as to adapt it to being swallowed. These 

 teeth are of various shapes, though usua^'y sharp 



* Attempts have been made to trace analogies between the 

 different segments of the jaws of fishes and corresponding parts 

 of the mouths of Crustacea and of insects : but the justness of 

 these analogies is yet far from being satisfactorily proved. 



