164 



BULLETIN 15 8, UNITED STATES NATIONAL MUSEUM 



basally, acuminate and fringed with minute hairs distally. Total 

 length, 1.1-1.2 mm. 



Male. — Body stout; genital segment neither dilated anteriorly nor 

 protuberant ventrally; caudal rami of normal size, their setae not 

 dilated ; fifth legs larger than in the other species, the right leg more 

 than twice as long as the left, its end segment slender, strongly 

 curved and clawlike ; second free segment much longer than the first, 

 with a very small inner protuberance. Total length, 1-1.1 mm. 



Reraarhs. — This species can be recognized by the size and shape 

 of the caudal rami in the female, together with the dilated bases of 

 the caudal setae and the ventral protuberance of the genital segment ; 

 in the male by the unequal length of the fifth legs. It does not seem 



to occur anywhere in such abun- 

 dance as is common for the other 

 species here enumerated. 



ACARTIA CLAUSII Giesbrecht 



FiGtJBE 112 



Acartia clansii Giesbrecht, Atti Ac- 

 cad. Lincei, Rome, ser. 4, vol. 5, 

 sem. 2, p. 25, 1889.— Sars, Crus- 

 tacea of Norway, vol. 4, p. 150, pi. 

 101, 1903. 



Occurrence. — Surface tow, Hy- 

 annis Harbor, Newport Harbor, 

 and Vineyard Sound by Rathbun ; 

 off the Bureau of Fisheries wharf 

 by Fish; surface tow. Station 

 10331, Gramp%iiS, by Bigelow. 



Dist7'ihution. — British Isles (T. 

 Scott, Cleve) ; coast of France 

 (Canu) ; Mediterranean, North 

 Atlantic (Giesbrecht) ; Black Sea 



(Karawajew) ; Azores, North Sea (Cleve) ; Norwegian coast (Sars) ; 



Alaska, Nova Scotia, Passamaquoddy Bay (Willey) ; Messina, Nizza 



(Claus) ; Malta, Canary Islands (Thompson) ; Adriatic (Car, 



Pesta) ; northern Atlantic (Cleve) ; Narragansett Bay (Williams) ; 



Chesapeake Bay (Wilson) ; Gulf of Maine (Bigelow) ; Woods Hole 



(Fish). 

 Golo7\ — So transparent and colorless as to be practically invisible 



over a white background, but with enough of a whitish cast to make 



them apparent over a black background (Rathbun). 



Fetnale. — No rostral filaments; corners of fifth segment without 



spines; genital and first abdominal segments with a row of small 



Figure 112. — Acartia clausii: a. Female, 

 dorsal (after Giesbrecht) ; i, female, 

 fifth legs ; c, male, fifth legs 



