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PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXVIII. 



Fig. 11. — First maxilliped of 

 Lepeophtheirus edwardsi. 



the first. Each is made up of two joints, the basal of which is much 

 swollen and liberally supplied with stout muscles, while the apical 

 one is a powerful claw curved over inward and carrying a spine 

 on its inner margin (fig. 12). 



These are the chief organs of prehension, 

 as already noted, and are usually much larger 

 in the male. Their relative size, however, 

 varies greathy in the different species and 

 genera; in one they are evidently the chief 

 reliance for clinging to the host or to the 

 female; in another the second antennae are so 

 much enlarged and the first maxilla? in the 

 male are so stout that these maxillipeds evi- 

 dently share the honors at the least. 



Lepeophtheirus innominatus is a good exam- 

 ple of the former, the basal joints of the second 

 maxillipeds being so large as to fill the cen- 

 tral portion of the carapace (Plate XXVIII). 

 And Caligus schistonyx is- a good example of 

 the latter, the terminal claw of the second maxillipeds being small 

 and very weak while the second antennas are large and stout (Plate VI). 



In many other species the 

 two are just about equal in 

 strength and efficiency. 



Between the swollen basal 

 joints of the second maxilli- 

 peds arises the furea or sternal 

 fork, which consists of a stout 

 chitin plate whose tip is bifid, 

 much like an old-fashioned 

 bootjack. 



It varies considerably in form 

 and relative size in the differ- 

 ent species, and for some au- 

 thors it serves on this account 

 as a secondary basis of classifi- 

 cation. It is frequently of con- 

 siderable service in this direc- 

 tion, and in one or two cases 



is sufficiently different to serve as the distinguishing characteristic of 

 the species. Witness the double bifurcation in Lepeophtheirus hip- 

 poglossi and L. Mfurcatus, and the peculiar form in the genus. Gloio- 

 potes and in Caligus platy tar si, and the entire absence of this append- 

 age in the genus Alebion (see Plates XX, XXIII). Several uses have 

 been suggested for the appendage. I. C. Thompson thinks that it 



Fig. 12.— The second maxillipeds or the adult 

 Caligus bonito. Upper figure, the male, with 

 A large bony plate on the basal joint; lower 

 figure, the female. 



