318 BULLETIN 15 8, UNITED STATES NATIONAL MUSEUM 



ment; rostrum bent downward and inward against the ventral sur- 

 face, and hence invisible dorsally ; cephalic segment almost twice the 

 length of the rest of the metasome. Fourth and fifth segments 

 strongly narrowed, the latter little more than half the width of the 

 former. Urosome two-thirds the length of the metasome; genital 

 segment as wide as the fifth segment anteriorly, then considerably 

 narrowed. Abdomen 3-segmented, the two basal segments about 

 equal in length, the anal segment longer. Caudal rami twice as long 

 as wide, the inner terminal seta as long as the urosome, the outer 

 seta attached to the center of the outer margin. Egg cases just 

 reaching the end of the abdomen, cylindrical in form and each con- 

 taining six or seven large eggs. 



First antennae 10-segmented, the jointing more or less indistinct, 

 and only half the length of the cephalic segment. Second antennae 

 4-segmented, the terminal segment tipped with six curved plumose 

 setae, the penultimate segment with a tuft of short setae at the distal 

 corner, the two basal segments with one seta each. Chewing blade 

 of the mandibles with the outer tooth larger than the others, which 

 diminish in size inwardly; palp biramose, inner ramus well devel- 

 oped, 2-segmented, outer ramus 4-segmented with weak setae. Sec- 

 ond maxillae with a digitiform lobe attached to the end of the basal 

 segment, and another on the second segment, the two terminal seg- 

 ments armed with setae. Maxillipeds made up of six segments, each 

 of the three basal segments with a lobe on its inner margin armed 

 with one or two setae, the terminal segment setiferous, the fourth 

 and fifth segments without setae. 



Rami of the swimming legs considerably widened, especially those 

 of the first pair, the terminal segment of the endopods not much 

 larger than the middle segmenjt and armed in the first legs with 

 four spines and three setae, in the other legs with five setae. The 

 terminal segment of the exopods is both wider and longer than the 

 middle and basal segments. In the first leg it is armed with four 

 spines and four setae, in the second and third legs with five spines 

 and three setae, and in the fourth leg with three spines and four 

 setae. These spines increase in length distally, and each is made up 

 of a stout central shaft, enlarged at its base, and wide smooth trans- 

 parent flanges on both margins. The spines on the basal and middle 

 exopod segments are like these on the end segments but smaller. 



The fifth legs are 2-segmented, the segments about equal in length 

 and in width, the basal one with a long seta at its outer distal cor- 

 ner, the terminal one with a stout inner spine, two outer spines, and 

 a terminal filiform seta. These spines are not flanged like those on 

 the preceding legs, but are perfectly smooth. The legs themselves 

 extend outward diagonally or nearly at right angles to the body 



