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PROCEEDINGS OF THE NATIONAL MUSEUM 



The character of the membranes, spines, and seta on the thoracic 

 legs is given below (for explanation of symbols, see figure 1): 



Caudal rami of female and male ovoid in general outline, width 

 slightly more than half the length in both sexes though male slightly 

 wider than female. Caudal rami of female shorter than abdomen, 

 longer than abdomen in male. Five plumose setae present, three 

 from distal surface, one from inner distal corner, one from outer 

 distal corner (figs. lSc,d). 



Remarks. — The significant characteristics of this species are the 

 ramified spines on the third segment of the first thoracic leg and the 

 multiramous spine on the first segment of the exopodite of the second 

 thoracic leg. 



The male of A. serratus, here described for the first tune, differs 

 significantly from the female only in the makeup of the second an- 

 tenna, the number of branches of the multiramous spine on the 

 first segment of the exopodite of the second thoracic leg, the character- 

 istic male feature of the fifth and sixth legs present on the genital 

 segment, the shorter abdomen, and the slightly larger caudal rami. 



As Shiino (1954) has indicated, this species could be placed in the 

 genus Lepeophtheirus were it not for the three-segmented fourth 

 thoracic legs: members of this genus have four-segmented fourth 

 thoracic legs. The fusion of the abdomen with the genital segment is 

 found in some members of the genus Lepeophtheirus; even in A. 

 serratus the abdomen of the male is distinctly separated from the 

 genital segment. The type species of the genus Anuretes, A. heckeli 

 (KoUar), has no distinct abdomen: it was for the members of the 

 family Caligidae with this characteristic, in addition to the segmenta- 

 tion of the fourth thoracic legs, that Heller (1865) erected the genus. 

 Since Heller's proposal of the genus, only one other species has been 

 placed in it that has no distinct abdomen {A. brevis Pearse, 1951), all 

 other species having a rudimentary or well-developed abdomen. 



