Description of a Species of Caligus. 233 



twelve. The outer margin of the dentated portion is provided 

 with a narrow corneous transparent edge. These mandibles ex- 

 tend backward and pass out of the buccal mass just anterior to the 

 lateral projection, c, (figs. 12 and 13,) and behind the process, f. 

 Here they are connected with a bony tendon, to which the large 

 muscles are attached which move the mandible. The mandibles 

 have no appendages, and are very slightly connected at their base 

 with the membranes of the buccal mass. When the buccal mass 

 is separated from the body by force applied below, the mandibles 

 invariably remain attached to their muscles. 



The remaining corneous organs at the extremity of the mouth 

 have been already described as connected with the lower mem- 

 brane ; the two pairs m, 1, on the surface of this membrane, and 

 the remaining, in its texture. The pair 1, have just been referred 

 to as seen through the opening between the lips. These bones 

 approximate at their apices ; at the other extremity they curve 

 backward and terminate under the junction of the two lips, (fig, 

 13, and a a, fig. 12;) the bones, m, which are situated under 

 the mandibles, are very finely pectinated on their outer margin ; 

 they terminate at the same place with the preceding pair. 



The remaining bones form a kind of frame work for the lower 

 membrane. Three slender bones r, s, t, (fig. 17,) occupy the 

 extremity of this membrane, and the bones, o, its inner portion. 

 The bones, o, extend backward and enlarge at the posterior part 

 of the buccal mass, (g, fig. 17,) where they serve for the attach- 

 ment of the muscles elevating the buccal mass. They appear to 

 form by their union at their anterior extremity, (figs. 17 and 13,) 

 a short, oblong process (k,) which is situated between the apices 

 of the pectinated bones, m. The piece, n (figs. 13 and 17,) passes 

 directly outward from this process, and is gradually lost in the 

 membrane. 



This complicated apparatus, the buccal mass, appears to be 

 composed of the upper and lower lips, united with the different 

 parts of a pair of maxillae. 



We have often observed through the upper membranes of the 

 buccal mass, and just in advance of the bony arch a, a, fig. 12, 

 an obscure curved line nearly concentric with the anterior mar- 

 gin of the buccal mass, (fig. 12,) which is frequently in motion. 

 From the peculiarities of its action we suppose that there is here 

 an internal opening to the esophagus. Within this inner mouth, 



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