•^Q£2 CRUSTACEA. 



The posterior antennae have usually two branches, and they termi- 

 nate in setae. 



The mandibular feet have a dentate mandible for the basal joint, 

 and a stout second joint, bearing commonly two short branches one- or 

 two-jointed, each ending in a tuft of setae. 



The first pair of maxillary feet are irregularly lobed, as shown in 

 the figures already referred to. The setulose setae, especially used for 

 maxillary purposes, proceed from one side of one or both of the first 

 two joints. The other setae are longer and generally plumose. 



The maxiUipeds are not branched. They are stout organs, either 

 straight or flexed, furnished on one side and at apex, with long setae 

 either naked or setulose. They are sometimes obsolescent, when the 

 following pair is much enlarged. 



The first pair of feet are either obsolescent, or long and slender 

 legs. When the former, they are sometimes two-branched, as in 

 figure 90, Plate 71, but when the latter, one branch is wanting and 

 the other is much enlarged, as seen in figures 82, 83. The last five 

 joints are shorter, and the setae, therefore, more crowded together in 

 83 than in 82. 



The posterior pair of cephalothoracic legs when developed are 

 either true natatory or subprehensile, as in figures 96 to 100, Plate 

 71. This prehensile character belongs only to the right leg of the 

 pair in males. Figures 94 and 96 belong to the same species, female 

 and male; 93 is female, and 100 male; 99 is another form of the 

 prehensile leg. 



The abdomen is always without appendages to the basal joint; the 

 number of joints is rarely over five and oftener it is four. It varies 

 somewhat even in the same species in its different states, and often 

 differs in the sexes ; and it is unsafe, therefore, to use it as a distinc- 

 tive character of species. 



Figures 101 to 104, and 108 to 110, Plate 71, are from different 

 Calanidae. The caudal stylets and setae are specifically constant, and 

 are an important means of distinction ; their varieties of form will be 

 observed in the figures alluded to, and in the various plates of species 

 of this family. 



The more prominent points of difference among the Calanidae, sug- 

 gesting a subdivision into subfamilies, are to be found in the first pair 

 of antennae and the eyes. The existence of an inferior eye, situated 



