574 CEPHALOPODA. 



Externally the jaws are imbedded to a considerable depth in a strong 

 mass of muscle (fig. 287, 6), composed of several layers of fibres variously 

 disposed, so as to open or close the jaws with a degree of force propor- 

 tioned to their large size. Here therefore is an apparatus fully ade- 

 quate to cooperate with the elaborately- constructed prehensile arms 

 whereby these predatory animals seize their prey ; and a victim once 

 involved in the tenacious grasp of the tentacula, and dragged to this 

 powerful beak, can have but little chance of resisting means of destruc- 

 tion so formidable as those granted to the Cephalopoda. 



(1538.) The mandibles of Nautilus Poinpilius, instead of being entirely 

 composed of horn (as is invariably the case in those genera that, being 

 provided with tentacula armed with suckers, are thus capable of seizing 

 active and slippery animals), would seem to be rather calculated to 

 break to pieces the testaceous coverings of Mollusca or the armour of 

 the Crustacea. They possess, indeed, the shape of the jaws already 

 described, but are blunt at their extremities (fig. 289, n, o), and thick- 

 ened by a covering of a dense calcareous substance ; so that they appear 

 manifestly adapted to crush hard substances rather than to cut or lace- 

 rate the tender bodies of fishes*. The jaws of the Nautilus, like those 

 of the Octopus above described, are imbedded in a powerful mass of 

 muscles (p) whereby they are opened and shut with great force, and 

 are also provided with a distinct muscular apparatus destined to pro- 

 trude them when in use, and again to retract the whole mass of the 

 mouth deeply into the body when unemployed. The mechanism pro- 

 vided for the protrusion of the mandibles is a strong semicircular muscle 

 (r r), which firmly embraces the base of the oral apparatus, and by its 

 contraction pushes it outwards among the labial tentacula (h, Ic) ; while, 

 on the other hand, four retractor muscles, the upper pair of which are 

 represented in the figure referred to (q q), arise from the extremities 

 of the cranial cartilage, and, running forwards to be inserted into the 

 oral mass, are the agents whereby the whole is again withdrawn and 

 thus concealed from view. 



(1539.) The tongue of the CEPHALOPODA, as in the Mollusca described 

 in the last two chapters, is an exceedingly important instrument, and 

 from its construction would here seem to be an organ of taste, as well 

 as a necessary assistant in deglutition. In the annexed figure, repre- 

 senting a vertical section of the beak of a very large Onychoteuthis, the 

 shape and disposition of the different parts of the tongue are well seen. 

 The substance of the tongue itself is fleshy (fig. 288, e, i), and its 

 movements are principally performed by the action of its own intrinsic 

 muscular fibres : its surface is divided into several lobes (f, g, h), par- 

 tially invested with a delicate and papillose membrane ; but a large 

 portion of the organ is covered with sharp recurved horny booklets, 

 so disposed that with their assistance the morsels of food taken into 

 * Owen, ' Memoir on the Pearly Nautilus.' London, 1832, 4to. 



