COPEPODS OF THE WOODS HOLE EEGION 311 



copepod groups. Accordingly, the fifth thoracic segment is here 

 regarded as belonging to the metasome, and the urosome includes 

 only the genital and abdominal segments. 



Family OITHONIDAE 



Genus OITHONA Baird, 1843 



Body slender, metasome moderately widened, urosome narrow, 

 almost linear, 4-segmented in female, 5-segmented in male; head 

 separated from first segment ; rostrum sharp-pointed in female, lack- 

 ing in male. First antenna 10- to 15-segmented ; second antenna 

 2-segmented, the terminal segment at right angles to the basal. 

 Kami of first four pairs of legs 3-segmented; outer exopod spines 

 lacking on the middle segment of the second and third legs, and 

 and on the two basal segments of the fourth leg; fifth leg a small 

 conical segment with a long apical seta, another long seta on the 

 side of the fifth segment in front of the leg. 



KEY TO THE SPECIES (BOTH SEXES ) 



1. Rostrum directed forward and visible in dorsal view ; first 



antennae reaching beyond genital segment 2 



Rostrum turned downward and invisible in dorsal view ; first 

 antennae not reaching beyond genital segment 3 



2. Basipods of first 3 and fifth legs, second segment of first antenna, 



and caudal rami with bright-colored plumose setae plujnifera (p. 311) 



These setae shorter and colorless, those on legs filiform, the 



others with minute plumes spinirostris (p. 312) 



3. End segments of first 4 exopods with 2, 1, 1, 1 in female, and in 



male, 2, 2, 2, and 2 outer spines, respectively similis (p. 314) 



End segments of first 4 exopods with 3, 3, 3, 2 in female, and in 



male 3, 3, 3, and 2 outer spines, respectively brevicornis (p. 315) 



OITHONA PLUMIFERA Baird 



FiGTJEB 187 



Oithona plumifera Baibd, The Zoologist (Newman), vol. 1, p. 59, 1843. — Gies- 

 BEECHT, Fauna und Flora des Golfes von Neapel, vol. 19, p. 537, pis. 4, 34, 

 44, 1892. 



Occurrence. — Two females were obtained in a surface tow south 

 of Marthas Vineyard, July, 1881. 



Distribution. — British seas (Baird) ; Mediterranean (Giesbrecht, 

 Pesta, Thompson) ; North Atlantic (Cleve) ; California coast 

 (Esterly) ; Malay Archipelago (A. Scott) ; North Sea, Arabian 

 Sea (Cleve) ; tropical Atlantic (Dana) ; Red Sea, Indian Ocean 

 (Thompson and Scott) ; Arctic Ocean (Mrazek) ; Adriatic (Car, 

 Graeffe, Steuer, Pesta) ; Cape of Good Hope (Cleve) ; Narragansett 

 Bay (Williams) ; Gulf Stream south of Marthas Vineyard 

 (Wheeler); Gulf of Maine (Bigelow) ; Chesapeake Bay (Wilson), 



