2322 CRUSTACEA. 



two pairs m, I, on the surface of this membrane, and the remaining, 

 in its texture. The pair ?, 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. p\ and a a, fig. p) ; the bones, 

 rn, 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 framework for the lower 

 membrane. Three slender bones, r, s, I (fig. p 5 )> occupy the extre- 

 mity 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.p 5 ), where they serve for the attachment of the 

 muscles elevating the buccal mass. They appear to form by their 

 union at their anterior extremity (figs, p* and p') a short, oblong 

 process (k), which is situated between the apices of the pectinated 

 bones, m. The piece n (figs. p l and/) passes directly outward from 

 this process, and is gradually lost in the membrane. 



We have often observed through the upper membranes of the 

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

 obscure curved line, nearly concentric with the anterior margin of the 

 buccal mass, which is frequently in motion. From the peculiarities 

 of its action, we suppose that there is here an internal opening to the 

 oesophagus. At this place, there are several folds seen below (fig./), 

 which may be the seat of the sense of taste. Above, we observe (fig. 

 p) four fleshy oblong organs extending from a point deeply situated 

 near the base of the oesophagus, obliquely upwards to the upper part 

 of the buccal mass. At their lower extremity, they are connected 

 by a slender ligament with the bone, g. These organs appear to close 

 the oesophagus. They often open and close in consequence of the 

 similar action of the processes, g, with which they are connected. 



The articulation of the buccal trunk with the surrounding parts is 

 formed by means of a bony process situated in it below/, and another 

 slender process (h, figs, p and p s ) extending backward and outward in 

 the adjacent teguments. A curved bony process (i, fig./) connects 

 the projection c (figs, f, p l ) with the process below/, uniting the two 

 portions of the buccal mass. 



In Argulus, the form of the trunk is nearly as in Caligus. The 



