76 



BULLiETIN 15 8, UNITED STATES NATIONAL, MUSEUM 



a large spine on the inner and a smaller one on the outer margin, 

 all four denticulate; anterior surface of the entire leg covered with 

 spines. Total length, 2-2.5 mm. 



Male. — Head strongly arched, without a crest; genital segment 

 no wider than the abdomen; urosome 4-segmented; anal segment 

 very short, but as wide as the penultimate segment; caudal rami as 

 wide as long, divergent; first antennae not reaching the posterior 

 end of the fifth segment; second antennae and mouth parts similar 

 to those of the female; endopods of swimming legs armed with 

 transverse rows of stout spines. Basipods of fifth legs 2-segmented, 



the second segment somewhat swollen and 

 armed at its outer distal corner with stiff 

 setae; exopods 2-segmented, proximal seg- 

 ment with a single spine on the outer mar- 

 gin, distal segment tipped with two unequal 

 spines, with a third shorter one on the inner 

 margin; the entire anterior surface of the 

 exopod is covered with stiff hairs. The 

 endopods are very rudimentary, each con- 

 sisting of a fingerlike process tipped with 

 three or four minute setae. Total length, 

 2.25 mm. 



Remarks. — A. Scott described and figured 

 an undeveloped male of Brachycalanus 

 gigas.) which is evidently closely related to 

 the one here presented, yet specifically dif- 

 ferent. Evidently no fully matured males 

 of this genus have thus far been found, and 

 the present is the first record of any species 

 of the genus upon American coasts. The 

 separation of the head and the fifth segment, 

 the very stout, slightly bifurcate, and 

 strongly chitinized rostrum, and the structure of the fifth legs furnish 

 distinguishing characters. 



Family SCOLECITHRICIDAE 

 Genus SCAPHOCALANUS G. O. Sars, 1900 



Head narrowed anteriorly, with or without a crest and com- 

 pletely fused with the first segment; fourth and fifth segments also 

 fused, with angular corners in the female, rounded in the male; 

 second inner caudal seta elongated; urosome 4-segmented in female, 

 5-segmented in male ; exopods of first four pairs of legs 3-segmented ; 

 first endopod 1-segmented, second endopod 2-segmented, third and 



Figure 51. — Brachycalanus 

 atlanticus: a. Female, 

 dorsal ; b, male, young, 

 fifth legs 



