136 PROCEEDINGS OF THE NATIONAL MUSEUM vol. us 



terminal process and bearing either naked or very lightly plumose 

 spinelike accessory process on inner sm-face, proximal to terminal 

 process. 



Thoracic legs I-III biramous, leg IV uniramous and poorly de- 

 veloped. For natiu-e of armatiu"e and legs, see table 14 and figm-e 35. 



Alebion gracilis Wilson, 1905 



FiGUBES 36a-c, S7a-d, 3Sa-e 



Alebion gracilis Wilson, 1905a/ p. 128; 1907a, p. 704, pi. IS, figs. 35-48; 

 1932, p. 420, fig. 264.— Shiino, 1959a, p. 316, figs. 19-21. 



Reported hosts. — Mustelus canis, Carcharias taurus, Carcharhinus 

 obscurus, Carcharhinus platyrhynchus, Carcharhinus lamiella, Sgualus 

 acanthias, "Tr7/gon" species, Pollachius virens, "Bonito." 



Distribution. — Revillagigedo Islands, Woods Hole Region. (Wil- 

 son, 1907a lists the cotypes as coming from Clarion Island, a member 

 of the Reviilagigedo Islands.) 



Material. — Three ovigerous and 2 nonovigerous adult females 

 (USNM 110S19) collected by Susumo Kato from the external siu-- 

 face of several specimens of sharks (no identification made) captured 

 by longline off Oahu, Hawaii. 



Measurements. — Five female specimens: 



Greatest length 



Greatest length of cephalothorax 



Greatest width of cephalothorax, excluding 



marginal flanges 

 Greatest length of genital segment, excluding 



posterior processes 

 Greatest width of genital segment 

 Greatest length of genital segment processes 

 Greatest length of abdomen 

 Egg string length (3 specimens) 



Diagnostic description of female. — Cephalothorax (fig. 36a) 

 ovoid, consisting of cephalic, maxilliped-bearing and first 3 pedig- 

 erous segments. Frontal region distinct, with narrow membranous 

 flange projecting posteriorly from anteroventral surface, lateral 

 cephalothoracic margins with distinct indentation at anterior end, 

 with narrow membranous flange extending along most of margin and 

 around broadly curved posterolateral cephalothoracic region, ter- 

 minating at beginning of U-shaped posterior sinus. Posterior sinus 

 with 2 membranes, 1 extending posteriorly from outer posterior end 

 of sinus, second extending along outer lateral margin. Posterior end 

 of median cephalothoracic region with 8 spines. Major dorsal 



^ The author used the name A. gracile but, in 1907a, corrected the improper 

 latinization of the term to A. gracilis. 



