COPEPODS OF THE WOODS HOLE KEGION 



295 



Fetnale. — Body rather slender, the margins of all the segments and 

 the surface of the abdominal segments with rows of fine hairs ; fifth 

 segment protruding dorsally, concave ventrally ; caudal rami longer 

 than wide, the inner apical seta twice as long as the outer. Basal 

 segment of first antenna the longest, divided posteriorly nearly to 

 its center; exopod of second antenna 2-segmented, its basal segment 

 with one seta, its distal segment with three setae. Endopods of first 

 four pairs of legs shorter than the exopods ; distal segment of third 

 endopod with six setae, of the other 

 three endopods with five setae; 

 fifth leg a 1-segmented lamina, 

 curved inward at its tip, and 

 armed with four plumose setae, 

 the outer one the longest. Total 

 length, 0.85-1 mm. 



Male. — Slightly smaller than the 

 female; the four basal segments 

 of the first antennae regularly ta- 

 pered, the fifth segment very short 

 but wider than the fourth, the 

 sixth segment swollen spherically 

 on its posterior margin, the seventh 

 segment transformed into a claw. 

 Swimming legs like those of the 

 female except the distal segment 

 of the second endopod, which car- 

 ries a small curved spine and only 

 two terminal setae. Fifth legs each 

 reduced to a short lamina fused 

 with the ventral surface of the 

 fifth segment and armed with 

 three setae, of which the middle 

 one is longer, the others shorter; 

 rudiments of a sixth pair of legs 

 are also present, each a small lamina with three setae 

 0.8-0.9 mm. 



Remarks. — This is a brackish-water species living close to the shore 

 among the seaweed, and the best place to look for it within the pres- 

 ent area will be in the brackish-water ponds, which are so numerous 

 along the shores of Cape Cod and on the various islands. The deep 

 cut in the basal segment of the first antennae and the structure of 

 the fifth legs are the best characters. 



Figure 180. — Tachidius Uttoralis: a, h, c, 

 Male, first, second, and fourth legs ; d, 

 female, fifth leg ; e, male, fifth and 

 sixth legs 



Total length, 



