150 U.S. NATIONAL MUSEUM BULLETIN 236 



2 setae at internal margin of 2nd endopodal segment of leg 4, proximal 

 seta very short. 



Leg 5 (fig. 55d) with smaU, broadly ovate exopodite, bearing 6 

 setae; no internal chitinous ridges or trabuculae present. Baso- 

 endopodite at apex truncate, reaching apex of exopodite; internal 

 margin straight, with number of chitinous ridges, external margin 

 spinulose. 5 marginal setae, 2 of which are lengthened. 



Specimens almost transparent, faintly greenish, without pigment 

 or eye. Female carries egg sac, fastened to genital somite by means 

 of yellow pad; ball composed of 10 eggs. 



Adult male, total length 0.39 mm.; length of longest furcal seta 

 0.30 mm. 



General appearance of the male same as the female but for the 

 following points : 



1. Proportional length of cephalothorax and abdomen is 17:9; 

 thorax more slender; cephalic somite with less produced lateral walls, 

 with the result that mouth parts are uncovered; epimeral plates of 

 thoracic somites 2 to 4 less produced, broadly rounded. Rostrum of 

 same appearance as in female, but heavier. 



2. Abdomen, at least in this specimen, less contracted, with the 

 result that whole appearance of animal is slenderer. Abdominal 

 somites 1 and 2 fully separate, fm'ca as in female. 



3. Antennules haplocerate, 9-segmented. Segments 1 and 2 

 fairly big, 3 and 5 small. Segment 4 only slightly swollen, with 

 distinct tooth. There is an asthetasc on segment 6, accompanied by 

 2 setae; the apical 3 segments (7-9) are small and slender (fig. 54d). 



4. Antenna, mouth parts and legs 1 to 4 as in female, with exception 

 of endopodite of leg 2, which is modified and 2-segmented. 1st 

 segment normally developed; 2nd segment with curiously formed 

 external and apical spines. In addition, there is a short external 

 seta and 2 long internal setae (fig. 54e). 



5. Leg 5 small, exopodite cordate, attached to baso-endopodite 

 with broad base, with 5 setae. Baso-endopodite rounded, reaching 

 apex of exopodite, with 3 setae (fig. 54/). 



Color as in female. 



Remarks. — The descriptions given above and the figures correspond 

 very well with Sars' account (loc. cit.) of this form. The variability 

 in length of the female is apparently considerable; Lang (1948, p. 546) 

 gives measurements of the female varying between 0.49 and 1.5 mm. 

 (the male is generally smaller than the female). SeweU's Pacific 

 female specimens measured 0.71 mm. The Ifaluk specimens are 

 exceedingly small, probably as a result of considerable contraction 

 during fixation. 



