352 



BULLETIN 15 8, UNITED STATES NATIONAL MUSEUM 



Figure 211. — Oncaea borealis: a. Female, lateral; 6, 

 female, urosome ; c, male, urosome 



Color. — Body transparent and colorless except for a faint tinge of 

 yellow, which is deepest around the mouth and in the bases of the 

 mouth parts and the swimming legs. 



Female. — Metasome fusiform, two and one-third times as long as 

 wide; second thoracic segment with a dorsal hump as in the pre- 

 ceding species. Urosome half the length of the metasome; genital 

 segment scarcely longer than the abdomen, and tapered posteriorly; 

 anal segment shorter than the two preceding segments combined; 



caudal rami much shorter 

 than anal segment. Fifth 

 leg rounded oval in form, 

 its apical setae about the 

 same length. Total 

 length, 0.6-0.7 mm. 



Male. — M u c h smaller 

 and more slender than 

 the female; second tho- 

 racic segment without a 

 dorsal hump ; urosome 

 much less than half the 

 length of the metasome; 

 genital segment very 

 large, three times the width and twice the length of the abdomen, 

 lappets at its posterior corners short, bluntly rounded, and extending 

 straight back ; maxillipeds larger than those of the female, the apical 

 claw smooth. Total length, 0.35-0.45 mm. 



Remarks. — Sars's separation of this species from conifera seems 

 perfectly valid, and the two may be recognized by the characters 

 given in the key above. This is more strictly a northern form, as is 

 expressed in its specific name, and it has never been found much 

 nearer the Tropics than in the present area. 



ONCAEA MINUTA Giesbrecht 



Figure 212 



Oncaea minuta Giesbrecht, Fauna und Flora des Golfes von Neapel, vol. 19, 

 p. 591, pi. 47, 1892. 



Occwrrence. — Both sexes were obtained in a vertical haul at a depth 

 of 1,000 meters, March, 1920, at Station 20069, Grampm, just south 

 of Georges Bank. 



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

 brecht) ; Indian Ocean (Thompson and Scott) ; Greenland coast 

 (Stephensen) ; coast of Norway (Sars) ; coast of California (Es- 

 terly) ; Chesapeake Bay (Wilson). 



Color. — Body semitransparent with a decided reddish tinge, deep- 

 est on the ventral surface ; eggs red ; eye not visible. 



