50 G PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxviii. 



It carries on its outer margin three claws of about the same length, 

 at the outer posterior corner a long plumose seta or a spine longer 

 than the claws, and on its posterior border three stout plumose setae. 

 Occasionally one of the terminal claws is developed at the expense of 

 the others, as in Lepeophtheirus monacanthus and L. quadratics and 

 Caligodes megacephalus. 



In the genus Gloiopotes two of the claws are curiously modified into 

 a three-pronged fork. 



One or two species have been reported in which there were no 

 plumose setae upon the posterior border ( Caligus hsemulonis and C. 

 productus). 



The endopod of these first legs is rudimentary and is represented in 

 some species by a minute joint bearing setae (Lepeophtheirus pectoralis) 

 and in others simply by the setae {Caligus rapax and C. honito). 



In the second pair of legs both exopod and endopod are well devel- 

 oped, two- or three-jointed, and plentifully supplied with plumose setae. 



Fig. 13. — First swimming leg of adult female Caligus bonito, ventral view. 



These latter point inward on either leg and are often long enough to 

 overlap on the mid line, thus forming a very effective swimming lam- 

 ina. These legs are almost exactly alike in all the genera. The large 

 basipod carries on its posterior margin a stout plumose seta, inclined 

 backward and inward at an angle of about 45°. The basal joint of the 

 exopod is longer than either of the other two joints and carries a plu- 

 mose seta on its inner margin and a stout spine at the outer distal cor- 

 ner (fig. 14:). The second joint is short, with a plumose seta on the 

 inner margin and a spine at the outer distal corner. The terminal 

 joint is almost circular in outline and carries a row of six plumose setae 

 around its edge and a spine at the outer corner. 



This exopod is in nearly the same line as the basipod, but the endo- 

 pod is bent inward until in Caligus and Lepeophtheirus it is at right 

 angles to the basipod, while in Gloiopotes and Alebion it is nearly par- 

 allel with it, but running in the opposite direction. The basal joint of 

 this endopod is short and carries a single plumose seta on its inner 

 margin. The second joint is the longest of the three and usually the 

 widest, and carries two plumose setae at its distal end. The circular 



