586 BULLETIN 159, UNITED STATES NATIONAL MUSEUM 



26. Caudal rami lamellar, half as long as urosome, divergent, with 



minute setae; second antenna no longer than first, claw short 



and straight; pelagic, 600 meters 9 Urocopia G. O. Sars, 1917 



Caudal rami cylindrical, little longer than anal segment, par- 

 allel, with long setae; second antenna much longer than first, 

 claw strongly curved; gi^ls of fishes. 



cf ? Ergasilus (part) Nordmann, 1832 (p. 375) 



27. Second antenna with 2 apical claws; first antenna 8-segmented, 



second segment longer than 4 end segments combined; caudal 

 rami twice as long as wide; parasitic on starfish. 



? Aatericola RosoU, 1888 

 Second antenna with 3 apical claws; first antenna 10-segmented, 

 segments equal; caudal rami five times as long as wide; fifth 

 legs wholly lacking; in an ascidian 9 Uperogcos Hesse, 1867 



28. Head fused with first segment; thorax with epimeral plates 29 



Head separated from first segment; thorax without epimeral 



plates 30 



29. Metasome with rounded epimeral plates; first antenna 10- 



segmented, first and sixth segments largest; each fifth leg 

 replaced by 3 stout ciliated spines; fresh water. 



& 9 Ectocyclops Brady, 1904 (p. 340) 

 Metasome with pointed epimeral plates; first antenna 9-seg- 

 mented, first and third segments largest; each fifth leg 

 replaced by 2 filiform setae (Antarctic Ocean) _ 9 Urogonia Brady, 1910 



30. Metasome pyriform, one-half longer than wide; first antenna 



8-segmented, more or less fused in female; fifth leg a knob 

 with 2 apical, 2 basal setae; surface, moderate depths. 



cT 9 Pachos Stebbing, 1910 

 Metasome of female short and squat, of male long and clavate; 

 first antenna 4-segmented and sparsely setose; fifth legs 

 wholly lacking; in compound ascidian. 



cf 9 Ophthalmopachus Hesse, 1866 



31. Second antennae prehensile, armed with strong curved claws 32 



Second antennae nonprehensile, armed with plumose setae 40 



32. Fourth segment of second antenna definitely longer than third 



segment 33 



Fourth segment of second antenna equal with third segment, or 



shorter 37 



33. Body cyclops-like, metasome four or five times as wide as 



urosome, its width half the body length; only slightly de- 

 pressed 34 



Body elongated, metasome but little wider than urosome, its 



width one-third the body length or less; strongly depressed 36 



34. Metasome three times as long as urosome; fifth leg with inside 



knob and outside seta at base, representing basal segment; 



dredged, moderate depths cf 9 Hermannella Canu, 1891 



Metasome less than twice as long as urosome; fifth leg without 



any trace of a basal segment 35 



