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BULLETIlSr 15 8, UNITED STATES NATIONAL MUSEUM 



legs ver}' narrow and elongate, those of the fourth pair reaching the 

 abdomen. Basal expansion of fifth legs not reaching the center of 

 the distal segment, with four apical setae, the second inner one plu- 

 mose and more than twice the length of the others, which are smooth. 



Distal segment five 

 times as long as wide, 

 with three apical 

 setae and three on the 

 outer margin ; the 

 inner apical one the 

 longest. Total length, 

 1.4-1.5 mm. 



Male. — First anten- 

 nae geniculate, 8-seg- 

 mented, the fourth 

 segment greatly elon- 

 gated and thickened, 

 the distal aesthetask 

 attached to the ante- 

 rior margin of the end 

 segment at its center. 

 The first endopod is 

 a little longer than 

 the exopod, its basal 

 segment almost twice 

 the length of the dis- 

 t a 1 segment, with 

 scattered hairs along 

 the inner margin and 

 a spine at the distal 

 corner. The second 

 endopod only reaches 

 the center of the sec- 

 ond exopod segment, 

 its distal segment 

 longer than the basal 

 segment, with one 

 apical plumose seta, 

 one inner filiform seta, and a group of three spines at the outer distal 

 corner. Basal expansion of fifth legs very short and tipped with two 

 setae; distal segment four times as long as wide, with three apical 

 and one outer seta. Total length, 1.16-1.3 mm. 



ReTTiarhs. — This is a pelagic species and belongs in tropical and 

 warm temperate regions, only appearing as an immigrant within the 



Figure 174. — Macrosetella gracilis: a. Female, lateral ; b, 

 male, first antenna ; c, male, fifth leg ; d, female, fifth 

 leg. (From W. M. Wheeler) 



