418 BULLETIN 15 8, UNITED STATES NATIONAL MUSEUM 



is three times as long as wide, the basal half stout, with convex sideia. 

 the branches slender and slightly curved. 



The basal segment of the first leg is armed onl}^ with a minute 

 filiform seta ; the endopod is much reduced, while the exopod is large 

 and stout, with three apical spines and a plumose seta. In the second 

 leg the first and second segments of the exopod have a spine at the 

 outer distal corner and a plumose seta on the inner margin, the end 

 segment has two spines on its outer margin and one on the ventral 

 surface, and five setae. The second segment of the endopod of the 

 second leg is prolonged inside the end segment, and terminates in two 

 setae. The endopod of the fourth leg is 2-segmented and just reaches 

 the distal margin of the second exopod segment; its basal segment is 

 unarmed, its end segment has two apical, one outer, and one inner 

 spine. The genital segment shows no leg rudiments. The egg strings 

 are rather slender and as long as the entire body. Total length, 

 8-9 mm. Width of carapace, 4—4.5 mm. 



Male. — Carapace like that of the female, with similar grooving; 

 the frontal plates are less prominent but the eye is larger and more 

 distinct. The dorsal plates of the fourth segment have a laioblike 

 projection at each anterior corner and no invagination on the outer 

 margins. The genital segment is elliptical, without posterior lobes 

 but with leg rudiments on the lateral margins just behind the center. 

 The abdomen is 2-segmented, the segments equal, the basal one with- 

 out posterior lobes ; the caudal rami are as wide as long, each tipped 

 with three setae. 



The terminal claw of the second antenna is turned down against 

 the ventral surface of the head, is bent into the shape of the letter U, 

 and has two small spines on its ventral surface near the base; the 

 second segment also has a spine on its ventral surface near the 

 posterior margin. Total length, 6-6.5 mm. Width of carapace, 

 2.5-3 mm. 



JRemarks. — This new species is very similar to hemipterm estab- 

 lished upon material obtained in Japan.^* The two can be distin- 

 guished by the frontal plates, the grooving of the carapace, the 

 relative size and shape of the dorsal plates on the fourth segment, 

 the posterior lobes of the genital segment, and the caudal rami. 



Genus ALEBION Kr0yer, 1863 



Carapace elliptical, as wide as long; no lunules; fourth segment 

 with dorsal plates in female, which are much reduced or lacldng in 

 male. Genital segment in female usually produced into a long proc- 

 ess at each posterior corner, extending backward beyond the tip of 



1* Proc. U. S. Nat. Mus., vol. 59. no. 2354, p. 4, 1921. 



