848 



BUI.LETIN 15 8, UNITED STATES NATIONAL MUSEUM 



of the fourth segment, but about the same length. Urosome half 

 as long as metasome, tapered posteriorly ; caudal rami a little longer 

 than the anal segment, six times as long as wide. First antennae 

 6-segmented, second segment the longest; end segment of second 

 antenna tipped with two stout curved claws and three long nearly 

 straight setae. The distal margin of the second basipod and the 

 outer margins of both rami of the first leg are fringed with stout 

 triangular spines. The fifth leg is 2-segmented, the distal segment 



three times as long as wide, 

 with a long apical, and two stout 

 outer, serrate spines, and a stalked 

 filiform seta on the dorsal surface 

 near the tip. Total length, 1.1- 

 1.3 mm. 



Male. — Much larger than the fe- 

 male, but of the same general shape ; 

 genital segment swollen and bear- 

 ing on each lateral margin a fringe 

 of spines and a single seta. Anten- 

 nae, mouth parts, and swimming 

 legs as in the female, except that a 

 pair of 2-segmented maxillipeds is 

 present, whose second segment is 

 swollen and armed with two rows 

 of tubercles and two setae on its in- 

 ner surface; the apical claw is 

 sickle-shaped, enlarged at its base, 

 and serrate on its inner margin. 

 Total length, 1.75-1.9 mm. 

 Remarks. — This is another species referred by Williams to the 

 genus Lichoinolgus, but which evidently belongs in the genus Myi- 

 cola., as shown by the general shape of the body, the parasitism upon 

 bivalve mollusks, the absence of maxillipeds in the female and the 

 presence of a stout pair in the male, the peculiar spines on the mar- 

 gins of the first legs, and the general structure of the fifth legs. 

 This species will probably be found in other localities in the southern 

 part of the present area, while the preceding species is the more 

 northern form of the same genus. 



Figure 208. — Myicola major: a. Female, 

 dorsal (after Williams) ; b, male, 

 maxilliped ; c, female, fifth leg 



Genus MACROCHEIRON Brady, 1872 



Metasome elliptical, a little more than half as wide as long; head 

 fused with first segment, one-half longer than rest of metasome; 

 urosome 4-segmented in female, 5-segmented in male; genital seg- 

 ment swollen anteriorly, sometimes divided; caudal rami longer 



