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BULLETIN 15 8, UNITED STATES NATIONAL MUSEUM 



OITHONA SIMILIS Clans 



Figure 189 



Oithona similis Claxjs, Die Copepodenfauna von Nizza, p. 14, 1866. — Sabs, 

 Crustacea of Norway, vol. 6, pp. 8, 207, pi. 3, 1913. 



Occw^ence. — Five hundred males and females were obtained in 

 a vertical haul at Station 10323, GraTtipus, northeast of Cape Cod 

 Light. A few specimens were obtained in Penzance Pond, Woods 

 Hole, August, 1926. 



Distribution. — Helgoland (Claus) ; Mediterranean (Giesbrecht) ; 

 Adriatic (Car, Pesta) ; North Atlantic (Cleve) ; Polar seas (Mrazek, 



Boeck) ; Antarctic Ocean 

 (Sars) ; Ked Sea, Indian 

 Ocean (Thompson and Scott) ; 

 Skager Rak, Arabian Sea, 

 Malay Archipelago (Cleve) ; 

 British seas (Brady) ; Canary 

 Islands (Thompson) ; coast of 

 Norway (Sars); Bohuslan 

 (Lilljeboro-, Trybom) ; North 

 Sea (Timm, van Breemen) ; 

 Gulf of Maine (Bigelow) ; 

 Narragansett Bay (Williams) ; 

 Woods Hole Harbor (Wheeler, 

 Fish); Chesapeake Bay 

 (Wilson). 



Color. — Body transparent 

 and often entirely colorless, 

 but sometimes with ferrugi- 

 nous pigment scattered spar- 

 ingly and irregularlj'^ through 

 both metasome and urosome; 

 eye deep red. 



Female. — Body only moder- 

 ately slender; rostrum turned 

 downward so as to be invisible dorsally ; urosome about three-fourths 

 the length of the metasome ; caudal rami much shorter than the anal 

 segment and divergent. First antennae not reaching the genital 

 segment; outer margin spines of the three exopod segments of the 

 first four pairs of legs: 1, 1, 2; 1, 0, 1; 1, 0, 1; 0, 0, 0, respectively; 

 ovisacs closely appressed to the sides of the urosome, each usually 

 with a single row of very large eggs. Total length, 0.7-0.95 mm. 



Male. — Rostrum entirely lacking; proportional lengths of the last 

 three abdominal segments as 10 : 8 : 9 ; middle segment no longer than 

 wide. First antennae twice geniculate, with a sheath just beyond the 



^^^^- 



FiGUHB 189. — Oithona similiB: a, Male, dorsal; 

 6, female, dorsal ; c, male, first antenna. 

 (From W. M. Wheeler) 



