362 CLASS CRUSTACEA. 



they are composed of six articulations, comprehending the 

 mobile finger of the forceps. These have an additional articu- 

 lation, and diflfer besides from the preceding, in having exter- 

 nally at their base, an arched appendage, inclining back- 

 wards, of two articulations, the last of which is compressed 

 and obtuse ; also their fifth articulation is terminated at the 

 internal side, by five small mobile leaflets, corneous, narrow, 

 elongated and pointed, and, moreover, the two fingers of the 

 forceps are mobile, or articulated at their base. The two 

 pieces situated in the interval of these feet, which M. Savigny 

 considers as a ligula, appear to me to be but two maxillary 

 lobes of these organs, but detached or free. The pharynx 

 occupies the interval comprised between all these feet. The 

 males are distinguished from the females by the form of the 

 forceps, which terminate the two or four anterior ones. They 

 are swelled, and destitute of the mobile finger. The last two 

 feet of this buckler are united, and in the form of a large mem- 

 branaceous leaflet, almost semicircular, supporting the sexual 

 organs at its posterior face, and presenting in the middle of 

 an emargination of the posterior edge, two small triangular 

 divisions, elongated and pointed, which appear to represent 

 the internal fingers of the forceps. Some sutures indicate 

 the other articulations. The second piece of the testa, arti- 

 culated with the preceding, at the middle of its posterior 

 emargination, and filling the vacancy which it forms, is 

 almost in the form of a triangle, truncated and emarginated 

 angularly at its posterior extremity. Its lateral edges are 

 alternately emarginated and denticulated, and the emargina- 

 tions, beginning from the second, present each in their 

 middle an elongated and mobile spine. There are six on 

 each side. In the inferior concavity are enclosed, and dis- 

 posed by pairs, ten fin-feet, almost similar, in form, to the last 

 two feet, but united simply at their base, applied one upon the 

 other, and supporting at their posterior face, the gills, which 



