COPEPODS OF THE WOODS HOLE KEGION 201 



abdomen with four segments. First antennae geniculate, the last 

 four segments turned forward; aesthetask at the end of the fourth 

 segment longer and larger than in the female. Second antennae, 

 mouth parts, and swimming legs similar to those in the female; in 

 the fifth legs the inner expansion of the basal segment is almost 

 obsolete and carries but a single seta; the outer apical seta of the 

 distal segment is elongated. There is also a sixth pair of legs on the 

 ventral surface of the genital segment behind the genital tubercles; 

 each is curved strongly outward and armed with four setae, the outer 

 one of which is larger than the others and extends beyond the lateral 

 margin of the segment. Total length, 0.7-0.8. Width, 0.2 mm. 



Remarks. — This is one of the most beautiful and graceful copepods 

 in the entire Woods Hole area, and it swims with all the ease and 

 agility of a cyclopoid. It was found in company with many other 

 harpactids and with Cyclops varicaris, and in its habits is far more 

 like the latter than like the former. 



Family THALESTRIDAE 



Genus THALESTRIS Claus, 1863 



Body stout and more or less deflexed ventrally; head fused with 

 first segment and laterally compressed, the epimeral portions turned 

 downward and including between them the mouth parts; epimeral 

 plates of second, third, and fourth segments thin and also turned 

 downward; urosome 4-segmented in female, 5-segmented in male; 

 genital segment only partially divided; caudal rami short and wide, 

 their apical setae very unequal. First antennae 9-segmented ; exopod 

 of second antennae 2-segmented; rami of first four pairs of legs 

 3-segmented; middle segment of first exopod and basal segment of 

 first endopod elongated ; fifth legs large and foliaceous in the female, 

 much smaller in the male. One species found here. 



THALESTRIS GIBBA (Kr0yer) 



Figure 133 



Harpacticus (/ibbus Ke0yer, Gaimard's voyage en Scaudinavie. Atlas, pi. 43, fig. 2, 



a-p, 1845. 

 Thalestris glbha Sars, Crustacea of Norway, vol. 5, p. 105, pi. 61, 1905. 



Occurrence. — Taken in large numbers in a surface tow by V. N. 

 Edwards in Woods Hole Harbor ; about 500 males and females were 

 obtained from boards under wharves at Fort Point, Gloucester, and 

 are now in the United States National Museum collection, showing 

 that it is even more numerous a little farther north. 



Distribution. — Franz Josef Land (T. Scott) ; Norwegian and Fin- 

 nish coasts (Sars, Kr0yer) ; Woods Hole (Sharpe). 



