120 BULLETIlSr 15 8, UNITED STATES NATIONAL. MUSEUM 



Distribution. — North Atlantic (Cleve) ; North Pacific (Gies- 

 brecht) ; coast of Norway (Sars) ; British Isles (Brady, Scott) ; 

 Mediterranean (Giesbrecht) ; South African seas (Cleve, Stebbing) ; 

 Gulf of Suez (Thompson and Scott) ; North Sea, Skager Rak 

 (Cleve) ; California coast (Esterly) ; Canadian coast (Willey) ; Gulf 

 of Maine (Bigelow) ; Woods Hole (Wheeler, Fish), 



Color. — Body transparent, with a whitish wash, so as to be visible 

 over a dark background, but almost invisible over a light background. 

 In alcohol the specimens assume a pure- white color without any red- 

 dish tinge (Rathbun). 



Female. — Posterior corners of fifth segment angular, but without 

 spines ; urosome, including the caudal rami, two-thirds as long as the 

 metasome; genital segment shorter than the abdomen; caudal rami 

 about twice as long as wide; first antennae only reaching center of 

 genital segment ; end segment of fifth legs with three apical setae and 

 a small spine on the outer margin; the inner apical seta is longest 

 and the outer one shortest, all sparsely plumose. Total length, 2.5-3 

 mm. 



Male. — Posterior corners of fifth segment as in the female; uro- 

 some relatively shorter and narrower; caudal rami scarcely twice as 

 long as wide; usually the left antenna geniculate; left fifth leg a 

 little shorter than the right, 5-segmented, the end segment longer 

 than the rest of the leg and not tapered distally, the second segment 

 with an inner fringe of hairs ; spinif orm process on inner margin of 

 third segment of right fifth leg denticulate distally. Total length, 

 2-2.5 mm. 



Reanarhs. — This is one of the three most abundant copepods of the 

 area, and is found in greater numbers at depths between 50 and 100 

 meters, swimming up to the surface at night and sinking again dur- 

 ing the day. It breeds within the area and increases regularly in 

 numbers in spring and fall, at which times it becomes of much 

 economic importance as fish food. The specimens referred by 

 Wheeler to Metridia hibemica really belong to this species. 



METRIDIA LONGA (Lubbock) 



FiGUEE 80 



Calanus longiis Lubbock, Ann. Mag. Nat. Hist., ser. 2, vol. 14, p. 127, pi. 6, 

 fig. 10, 1854.— Sars, Crustacea of Norway, vol. 4, p. 112, pis. 75-76, 1902. 



Occvfrrence. — One hundred males and females from the trawl 

 wings, Stations 1027, 1039, 1089, Fish Hawk, south of Nantucket, and 

 Stations 2195, 2236, Albatross, off Marthas Vineyard; four females 

 by Rathbun in surface tow in Woods Hole Harbor, August, 1883; 

 many hundreds obtained in surface tows at 20 Gra77ipus stations, 

 and in vertical hauls at 55 Grampus stations in the Gulf of Maine. 



