72 BRITISH KVro.MOSTRAC.A. 



rather of a complicated .structure, is situate near the junc- 

 tion of the head and body, near the base of the beak, and 

 consists, according to Straus, who has given the most 

 correct account of this organ, of a labrum or lip, two man- 

 dibles, and one pair of jaws. The labrum or lip (f. B, 

 y, and f. c) consists of a flattish body, compressed at the 

 sides, and has at its extremity a large lobule, furnished 

 with several set;r. It is fixed 1o the posterior part of the 

 base of the beak, is very moveable upon its antero-supcrior 

 angle, and by means of powerful muscles ({'.<;,#, b, c] admits 

 of a considerable separation. 



The mandibles (f. n) are very strong, and consist each 

 of a stout fleshy-looking body, which, at its superior extre- 

 mity, is in form of a narrow point, and articulates there 

 by means of several muscles with the body (f. A,/). It 

 descends from thence vertically to the mouth, its inferior 

 extremity being curved sharply inwards, so as to penetrate 

 into the mouth between the lip and corresponding jaw, 

 and terminates in a free unattached edge, which has appa- 

 rently neither teeth nor triturating surface, but which 

 when pressed closely between two pieces of glass, may he 

 observed to be provided with a series of about eight .small 

 teeth, slightly curved. These mandibles are not pro\ ided 

 with either palpi or branchiae, but are quite naked, and 

 are moved by two muscles; an abductor, which moves 

 them upon themselves from within outwards, and an 

 adductor, which brings them back to their first position, 

 at the sain;' tune bringing them nearer, each to the other. 

 The motion of tlu>e organs, when the animal is feeding, 

 is semi-rotatorv. 



i 



The jaws if. A, n, /;, and f. r) consist each of a strong- 

 body, somewhat rounded on the anterior surface, and 

 terminated b\ four strong horny spines, three of which 

 are prolonged into hooks, strongly curud forwards and 

 inuards. The fourth being small and stiaight. These 

 parts seem to lie constantly in motion, as if the animal 

 \\ere perpetually cniplo\ed ill eating. The mouth, as I 

 have alread} slated. \\as placed by Swannnerdam at the 



