COPEPODS OF THE WOODS HOLE REGION 



239 



first legs and by the fifth legs of both sexes. It has never before been 

 reported from American localities, but it is likely to be found in any 

 of the brackish ponds of the present area. 



MESOCHRA PYGMAEA (Claus) 



Figure 159 



Dactyloims pyginneus Claxts, Die frei lebenden Copepoden, p. 127, pi. 17, 1863. 

 Mesochra pygmaca Sars, Crustacea of Norway, vol. 5, p. 209, pi. 136, 1907. 



Occurrence. — Seventy-five specimens, including both sexes, were 

 washed from the sand on the shore of Katama Bay, Marthas Vine- 

 yard, August, 1927. 



Distribution. — Helgoland (Claus) ; Scottish coast (T. Scott) ; 

 Polar seas (T. Scott) ; Norwegian coa,st (Sars). 



Color. — Body brownish or grayish yellow and only semitrans- 

 parent; eggs dark cinnamon-brown; eye minute and reddish. 



Female. — Body comparatively short 

 and stout, tapered posteriorly, the meta- 

 some passing insensibly into tlie uro- 

 some; cephalic segment as long as the 

 rest of the metasome and the widest part 

 of the body; genital segment only later- 

 ally divided; caudal rami wider than 

 long, both apical setae jointed near their 

 base. First antennae 6-segmented, three 

 terminal segments nearly as long as three 

 basal; first endopod twice the length of 

 the exopod, middle segment of latter 

 without an inner seta; basal expansion 

 of fifth legs narrow and just reaching the tip of the distal segment, 

 with five setae, the second outer one very long; distal segment as 

 wide as long, obliquely truncated, with five setae, the second inner 

 one elongated. Total length, 0.35-0.4 mm. 



Male. — Terminal segment of second endopod with a stout spine 

 near the base and two unequal apical setae ; basal expansion of fifth 

 legs reaching little beyond the center of the distal segment, with 

 two ^ubequal setae ; distal segment constricted at the base, with five 

 setae, the middle one the longest, the two outer ones very weak. 

 Total length, 0.33-0.38 mm. 



RetnaThs. — This species is scarcely half the size of the preceding 

 one ; its integument is exceptionally hard and smooth, and this makes 

 it difficult to dissect. The first endopods and the fifth legs are the 

 best means of identification, coupled with its very small size. It is 

 here reported for the first time from American coasts, and was fairly 

 abundant in the one locality. , 



Figure 159. — Mesochra pyg- 

 maea: a. Female, fifth leg; 

 t, male, endopod of third 

 leg ; 0, male, fifth leg 



