98 BULLETIN 15 8, UNITED STATES NATIONAL MUSEUM 



spines on each side ; genital segment longer than the abdomen ; caudal 

 rami fringed with cilia on their inner margins; spines on basipods 

 of fifth legs large, protruding beyond the lateral margins; setae on 

 second basipod minute and hairlike ; endopod much longer than basal 

 segment of exopod, tipped with two subequal spines and a sharp 

 inner process, fringed with cilia; hook on second exopod segment 

 smooth; third exopod segment represented by two spines, the inner 

 the longer. Total length, 1.4-1.6 mm. 



Male. — Urosome sometimes symmetrical, sometimes twisted to the 

 right; grasping antenna considerably swollen; posterior corners of 

 fifth segment angular but without spines; second basipod of right 

 fifth leg twice as long as wide, with convex lateral margins ; endopod 

 a rudimentary curved process on inner margin of second basipod, 

 near the distal end; second exopod segment one-half longer than 

 first, the lateral spine near the tip ; end claw stout and setose on the 

 inner margin distally; rami of left fifth leg equal, endopod 2-seg- 

 mented, spatulate, its inner margin crenate, exopod tipped with a 

 curved spine and a finger process, both setose. Total length, 1.25- 

 1.35 mm. 



Remarks. — The fifth legs are peculiar in both sexes and will serve 

 to identify the species. In 75 per cent of the specimens from the 

 two ponds in Bourne the urosome of the female was twisted to the 

 left and that of the male to the right. The species will probably be 

 found elsewhere on the cape and on Marthas Vineyard, as the ponds 

 are more thoroughly examined. 



DIAPTOMUS BIRGEI Marsh 



FlGUEB 66 



Diaptomus birgei Marsh, Trans. Wisconsin Acad. Sci., vol. 9, p. 16, pi. 1, figs. 

 4-6, 1894 ; vol. 15, p. 435, pi. 18, figs. 6, 8, pi. 19, figs. 1, 6, 1907. 



Occurrence. — Both sexes found in abundance in a small lily pond 

 just south of Falmouth Arms Hotel, on the east shore of Buzzards 

 Bay; a small lily pond north of Nobska Lighthouse; Crockers Pond, 

 Falmouth ; Ice Pond, Quisset, Falmouth ; Flax Pond, Falmouth. 



Distribution. — Wisconsin (Marsh) ; Indiana (Juday, Marsh) ; 

 Cold Spring Harbor, Long Island (Pratt) ; Washington, D. C. 

 (Marsh) ; North Carolina (Coker) ; Ontario, New Brunswick 

 (Klugh). 



Color. — Body transparent, washed with light blue, which is deep- 

 ened into a dark-blue stripe along the posterior margins of the meta- 

 some segments; distal half of first antennae and the first four pairs 

 of legs orange; fifth legs and bases of the other four pairs dark 

 blue ; oviducts and eggs reddish brown ; eye blue. 



