466 BULLETIN 15 8, UNITED STATES NATIONAL MUSEUM 



terior end of these ventral plates is visible in dorsal view on either 

 side of the segment behind the dorsal plate, and each is tipped with 

 one long and two very short setae. The abdomen is 4-segmented, the 

 basal segment the widest and as long as the second and third seg- 

 ments combined ; the anal segment is a little longer than the penulti- 

 mate segment. The caudal rami are elliptical, laminate, one-half 

 longer than wide, and each is tipped with three plumose setae. 



The first antennae are like those of the female, very indistinctly 

 jointed in the basal half, but apparently made up of 12 segments. 

 The second antennae and mouth parts correspond to those of the 

 female; the maxillipeds are relatively larger but show similar de- 

 tails. In the swimming legs the terminal segments, especially of 

 the endopods, are relatively longer, and both rami are armed with 

 plumose setae as well as spines. The arrangement of the spines and 

 setae is as follows: Second exopod, 1-1, 3-4; second endopod, 1-1. 

 0-6; third exopod, 1-1, 3-5; third endopod, 1-1, 1-4; fourth exopod, 

 1-1, 3-7; fourth endopod, 1-1, 1-4. The spine on the terminal en- 

 dopod segment of the third and fourth legs is not at the outer corner, 

 but between the two outer setae; it is bent upward away from the 

 plane of the four setae and is somewhat hooked at the tip, and thus 

 forms an effective clasping organ. The fifth leg is a 1-segmented 

 lamella, nearly as wide as long, and tipped with three medium-sized 

 plumose setae. Total length, 4-5 mm. 



ReTrmrks. — This is the commonest species in the area, as evidenced 

 by the number of specimens obtained and the variety of hosts. It 

 may be determined by the smooth lateral margins of the second seg- 

 ment, and the absence of lobes at the posterior corners of the fourth 

 segment. 



Genus EUDACTYLINA Beneden, 1853 



Female. — Head fused with first segment; four free segments with 

 dorsal plates; genital segment smaller than fifth segment, oviduct 

 openings ventro-lateral ; abdomen 2-segmented; caudal rami lami- 

 nate, with nonplumose setae. First antenna usually 5-segmented, the 

 terminal portion (three segments) at right angles to the basal, both 

 portions heavily armed with spiny claws. Second antenna 3-seg- 

 mented, with one or more apical claws ; first maxilla deeply bilobed, 

 with spiniform setae; second maxilla 3-segmented, with a pectinate 

 apical claw; maxillipeds large, with a stout vertical chela made up 

 of two digits, the tip of one shutting into the tip of the other. First 

 four pairs of legs biramose, rami of first pair 2- or 3-segmented, of 

 the other pairs 3-segmented, except the fourth endopod, which is 

 sometimes 1-segmented ; fifth legs uniramose, lamellar, wholly visible 

 in dorsal view. 



