JAWS OF INSECTS. 95 



the wound is inflicted, tlic teeth, heing moveahle at their 

 base, fall back, leavinp; the openini^ of the mouth free for 

 sucking. The wound thus made is of a peculiar form, being 

 composed of three lines, radiating from a centre, where the 

 three teeth had penetrated. 



Most of the Mollusca which inhabit univalve shells are 

 provided with a tubular organ, of a cylindric or conical 

 shape, capable of elongation and contraction, by circular and 

 longitudinal muscular fibres, and serving the purpose of a 

 proboscis, or organ of prehension, for seizing and conveying 

 food into the mouth. These tubes are of great size in the 

 Bucciniim, the Miirex, and the Valuta, as also in the 

 Doris, which, though it has no shell, is likewise a gastero- 

 pode. In those mollusca of this order which have not a 

 proboscis, as the Limax, or slug, the Helix, or snail, and 

 the ^plysia, or sea-hare, the mouth is furnished with broad 

 270 lips, and is supported by an internal cartilage, 

 iSfl^ having several tooth-like projections, which assist 

 in laying hold of the substances taken as food. 

 That of the snail is represented in Fig. 270. 



All the Sepiss, or cuttle fish tribe, are furnished, at the 

 entrance of the mouth, with two horny jaws, having a re- 

 markable resemblance to the bill of a parrot; excepting that 

 the lower piece is the larger of the two, and covers the up- 

 per one, which is the reverse of what takes place in the 

 parrot. These constitute a powerful instrument for break- 

 ing the shells of the molhisca 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 principally as organs of 

 prehension and detention; and the upper jaw, as well as the 

 lower one, being moveable upon the cranium, they are ca- 

 pable of opening to a great width. The bony pieces which 

 compose the jaws are more numerous than the correspond- 

 ing bones in the higher classes of vertebrata, and tlicy ap- 

 pear, therefore, as if their development had not proceeded 



