COPEPODS OF THE WOODS HOLE REGION 



321 



Color. — Body only semitransparent, with an olive-p:reen tinge; 

 ovaries and oviducts dark blue and showing distinctly in both dorsal 

 and ventral views; eggs grayish white, each with a light-brown 

 center; eye reddish. 



Female. — Cephalic segment considerably more than half the length 

 of the metasome, second, third, and fourth segments narrowed regu- 

 larly, Avith rounded epimeral plates, fifth segment abruptly reduced 

 to half the width of the fourth segment and without plates. Uro- 

 some half the length of the metasome; caudal rami twice as long 

 as wide and divergent. First antennae 6-segmented, the fourth seg- 

 ment longer than the fifth and sixth combined; terminal segments 

 of the exopods of the first three pairs of legs with three outer spines, 

 of the fourth legs with only two outer 

 spines ; second inner seta on distal seg- 

 ment of fifth legs filiform, the others 

 plumose. Total length, 0.6-0.85 mm. 



Male. — Much smaller than the fe- 

 male; first antennae twice geniculate, 

 composed of at least 11 segments, some 

 of which are very indistinctly defined. 

 The middle section is only slightly 

 swollen and the terminal section is 

 sharply pointed. The first four pairs 

 of legs are like those of the female ; in 

 the fifth legs the basal segment is 

 more distinctly defined and the ter- 

 minal segment is narrower, with 

 longer and more slender setae. In all 

 the males examined this segment had 

 only four setae, all plumose, and one 

 of these was apical. Sars said that 

 this segment in the male differed from that in the female "by the 

 presence of an additional seta attached inside the others." ^^ In his 

 figure of the male fifth leg he showed a filiform seta as apical; the 

 males here recorded had no filiform seta on the fifth leg. 



Remarks. — This is a brackish-water species. Marsh reported it as 

 having been collected in Lake Pontchartrain, Louisiana, and added : 

 " It seems likely that further collections in brackish w^at^rs will 

 show that this is not an uncommon form." ^^ The localities here 

 given abundantly support that statement, and prove also that it is 

 not confined to the Southern States. 



Figure 191. — Halicvclops magni- 

 ceps: a. Female, dorsal; 6, fe- 

 male, fifth leg ; c, male, fifth leg 



" Crustacea of Norway, vol. 6, p. 30, 1913. 



12 Trans. Wisconsin Acad. Sci., vol. 16, pt. 2, no. 3, p. 1106, 1910. 



