COPEPODS OF THE WOODS HOLE REGION 101 



as wide, with an angular process at the inner distal corner and a 

 spine at the outer corner; terminal claw twice as long as second 

 segment, setose at the center of the inner margin; left endopod tri- 

 angular, as long as first exopod segment; second exopod segment 

 produced into two processes at the tip, the outer one fingerlike, the 

 inner one wider and bifid. Total length, 1.25-1.4 mm. 



Development stages. — In the undeveloped female the endopods of 

 the fifth legs are as long as the entire exopod, pointed at the end with- 

 out spines or setae ; the first exopod segment is but little longer than 

 the second and no wider ; the second segment carries a large spine on 

 the inner margin, two smaller ones at the tip, and a tiny one on the 

 outer margin. In the undeveloped male the left leg is almost as 

 long as the right ; each endopod is very stout, cylindrical, and longer 

 than the first segment of the exopod; the two segments of each 

 exopod are about equal in length, the end segment armed with a 

 long straight terminal spine and a much shorter one on the outer 

 margin. 



Remarks. — ^A ripe female carries usually six eggs, one in the center 

 and the other five in a circle around it, all in the same plane. This 

 species is extremely abundant in some of the first lakes mentioned 

 above, thousands being obtained in a single haul of the net. Accord- 

 ing to Marsh it is one of the most widely distributed North American 

 species, and may be recognized by the form of the fifth legs. 



Genus PSEUDODIAPTOMUS Herrick, 1884 



Head fused with or separated from the first segment; posterior 

 corners of fifth segment rounded, fringed with hairs in the female, 

 naked in the male; caudal rami at least two and one-half times as 

 long as wide; genital segment of female considerably swollen, with 

 patches of spines and bristles arranged asymmetrically ; rami of first 

 four pairs of legs 3-segmented ; fifth legs uniramose in female ; right 

 fifth leg in male uniramose, left biramose; female with two egg 

 sacks, the right one much smaller than the left, rarely lacking. A 

 single species. 



PSEUDODIAPTOMUS CORONATUS Williams 



FiGUBE 68 



Pseudodiaptomus coronatus Williams, Amer. Nat., vol. 40, p. 641, figs. 1-7, 

 1906. 



Occurrence. — One hundred males and females, surface tow. Woods 

 Hole Harbor, September, 1882; 10 males and females, surface tow, 

 Cuttyhunk Harbor, July, 1925; 2 males,' surface tow, pond No. 2, 

 Chappaquiddick Island, July, 1926; 150, both sexes, surface tow, 



