96 BULLETIN 15 8, UNITED STATES NATIONAL MUSEUM 



antennae reaching tip of caudal rami 5 first basipod segment of fifth 

 legs considerably swollen, with a small ventral spine ; second basipod 

 with a minute lateral seta ; second exopod segment with smooth mar- 

 gins ; third segment' represented by two stout spines, the outer one 

 the smaller; a third spine on the outer margin of the second seg- 

 ment. Total length, 1.5-1.9 mm. 



Male. — Smaller than female but similar in color and general de- 

 tails. Right antenna much swollen anterior to the geniculating seg- 

 ment; a narrow hyaline membrane on the antepenultimate segment, 

 prolonged slightly at the distal end into a small knob. First basipod 

 of fifth leg with a small ventral spine; second basipod of right leg 

 quadrangular, twice as long as wide, with a shelf-like projection on 

 the posterior surface near the distal end, from which arises a blunt 

 curved hook. Second exopod segment 4 times as long as wide, 

 with a small process at its base inside and a lateral seta outside near 

 its tip. The apical spine is slender, nearly straight, and denticulate 

 on its inner margin. The right endopod is slender and a little longer 

 than the basal segment of the exopod, tipped with minute setae and 

 fine hairs. The left exopod is 2-segmented, the second segment much 

 narrower than the first, with an apical plumose seta and a dactylose 

 process; left endopod longer than basal segment of exopod, and 

 tipped with fine hairs. Total length, 1.25-1.5 mm. 



Developmient stages. — In a young female 1 mm. long the basipod 

 segments of the fifth legs are comparatively larger, while the rami 

 are 1-segmented and reduced in size. The exopods are a half longer 

 than the endopods and each of the 4 rami is armed with two apical 

 setae of about the same length. The endopod has an invagination 

 near the center of the outer margin, indicating its approaching divi- 

 sion, but there is no sign of the long spine, which appears on the 

 second segment in the adult. The two setae at the tip of the exopod 

 represent the third segment in the mature adult, and the minute spine 

 which appears behind them in the adult belongs to the second seg- 

 ment. 



In a young male 1.25 mm. long the left fifth leg is nearly as long 

 as the right ; the endopods are cylindrical, reaching to the middle of 

 the second exopod segment and tipped with several minute setae and 

 hairs. The exopods are 2-segmented, the distal segment longer than 

 the proximal, considerably tapered, with a rather stout apical spine 

 and a much smaller one on the outer margin. This male had already 

 reached the minimum size for adults and would probably have had 

 but one more molt before assuming the adult form. Hence the 

 fifth legs undergo considerable metamorphosis even in the last molt. 



Remarks. — This is the most highly colored copepod in the present 

 area and may be recognized by that fact alone; the details of the 



