224 BULLETIN 15 8, UNITED STATES NATIONAL MUSEUM 



Color. — Urosome transparent, with a bluish tinge, metasome whit- 

 ish and more opaque ; mouth parts and swimming legs with a brown- 

 ish wash; eggs white and opaque; eye pale blue. 



Female. — Body narrow-elongate, nearly the same width through- 

 out and five times as long as wide; head completely fused with the 

 first segment, the resultant cephalothorax a little less than half 

 the length of the metasome ; second segment a little longer than any 

 of the three following segments, which are about equal. 



Urosome two-thirds as long as metasome; genital segment dis- 

 tinctly divided, the posterior portion longer than the anterior. 

 Nearly every female carries a single spermatophore attached to the 

 ventral surface of the anterior portion of the genital segment. This 

 spermatophore is cylindrical and is coiled into a circle, and both ends 

 are attached to the segment, reminding one somewhat of a spare tire. 

 Abdomen made up of three segments, diminishing slightly in length 

 and width posteriorly. Caudal rami nearly twice as wide as long, 

 the outer apical seta considerably longer than the inner. 



First antennae 8-segmented and evenly divided between the basal 

 and terminal portions; second antennae of the usual pattern, with a 

 3-segmented exopod. Rostrum long and narrow and rather bluntly 

 pointed, with a distinct ventral keel. In the first legs the basal seg- 

 ment of the endopod is only a little longer than the entire exopod, 

 and carries a large plumose seta on its inner margin near the distal 

 end. The two distal segments combined are two-thirds as long as 

 the basal segment, and the third one is three times as long as the 

 second, and tipped with two subequal setae. The spine at the inner 

 corner of the second basipod is more than one-third the length of 

 the basal endopod segment. The three exopod segments are about 

 equal in length, the two basal ones each carry a long spine on the 

 outer margin, the end segment carries two long spines at its outer 

 distal corner and two apical setae, slightly geniculate. The three 

 following pairs of legs are of the usual pattern in this genus; distal 

 segments of third exopod with four spines and two setae. Inner 

 expansion of basal segment of fifth legs broadly triangular, with two 

 unequal apical, and three inner setae, all the latter plumose. Distal 

 segment elongate oval, narrowed at its tip, with six setae, the second 

 and third inner ones filiform and elongated. Total length, 0.75- 

 0.85 mm. 



Male. — Somewhat smaller than the female but otherwise of the 

 same appearance. First antennae geniculate, the fourth segment 

 considerably swollen and armed with an aesthetask as long as the 

 four basal segments combined; the terminal portion of four seg- 

 ments is usually coiled into a small circle, with the terminal segment 

 below the fifth segment. In the first legs the second basipod is 

 armed on its inner margin with three wide, acute spines, short and 



