102 



BULLETIN 15 8, UNITED STATES NATIONAL MUSEUM 



Gosnold Pond, Cuttyhunk Island, July, 1926; 6 males and females, 

 surface tow, Great Pond, Falmouth, July, 1925; 1 female. Great 

 Pond, Barnstable. 



Distribution. — Narragansett Bay (Williams); Woods Hole 

 (Sharpe, Fish); Nova Scotia (Willey) ; Chesapeake Bay (Wilson). 



Color. — Body a dingy white, sometimes continuous, sometimes with 

 a colorless band across the center; in formalin the females become 

 blue, especially around the digestive canal and the bases of the ap- 

 pendages, and the abdomen is spotted with small blue dots, but the 

 eggs become orange. 



Female. — Head separated from first segment and fifth segment 

 from the fourth; urosome 4-segmented, more or less asymmetrical; 



FiGDRB 68. — Pscudodiaptomus coronatus: a. Female, lateral, showing inequality 

 of the two egg-cases ; b, female, fifth legs ; c, male, fifth legs ; d, yonng male, 

 fifth legs 



genital segment protruding ventrally, with a pair of spatulate flaps 

 over the genital aperture ; first abdominal segment with a depression 

 on the left side, filled with stout bristles; caudal rami five times as 

 long as wide, slightly asymmetrical; fifth legs 4-segmented, each 

 tipped with a curved spine denticulate on the inner margin, and at 

 its base on the inside a toothed lamella; two ovisacs, the right one 

 containing only two eggs, sometimes entirely lacking. Total length, 

 1.25-1.5 mm. 



Male.- — Body shorter and more slender; urosome 5-segmented, 

 symmetrical ; genital segment with a fringe of setae along the dorsal 

 posterior margin and a semicircle of setae on the ventral surface; 

 abdominal segments with triangular spines on their posterior mar- 

 gins; right fifth leg uniramose, 4-segmented, tipped with a curved 

 claw and a stout plumose. seta; left leg biramose, first basipod seg- 

 ment with a cluster of finger spines on its inner margin, second seg- 



