COPEPODS OF THE WOODS HOLE REGION 607 



22. Abdomen much shorter than genital segment, its 2 segments 



about the same length; genital segment less than half as wide 

 as carapace; outside of fishes. cT ? Elytrophora Gerstaecker, 1853 (p. 416) 

 Abdomen twice as long as genital segment, its basal segment 

 10 times as long as terminal segment; genital segment wider 

 than carapace; gill cavity of fishes. 9 Euryphorus Milne Edwards, 1840 



23. First legs uniramose, others biramose; 2 pairs of dorsal thoracic 



plates, 1 on fused second and third segment, 1 on fourth 



segment; outside of sharks 9 Pholidopus Wilson, 1907 



All 4 pairs of legs biramose; thorax with or without dorsal plates 24 



24. One to four pairs of dorsal plates; abdomen 1-segmented and 



wholly concealed in dorsal view 25 



No dorsal plates; abdomen 1- or 2-segmented and wholly visible 



in dorsal view; males only 39 



25. Rami of first 4 pairs of legs with same number of segments, and 



all of them armed with plumose setae or spines, or both 26 



Rami of first 4 pairs of legs differing in number of segments, 



some or all of them destitute of setae and spines 27 



26. Rami all 3-segmented; 4 pairs of dorsal plates, first and third 



pairs median, second and fourth lateral; second pair widely 



separated, fourth fused; outside of shark ? Lepimacrus Hesse, 1883 



Rami all 2-segmented; 1 pair of dorsal plates on fourth segment 

 in female, none in male; abdomen 1-segmented; caudal rami 

 very large, setae short; outside of shark cf ? Demoleus Heller, 1865 



27. Rami of first 3 pairs of legs 2-segmented, of fourth pair 



1-segmented 28 



Rami of first 2 pairs 2-segmented, of third and fourth pairs 



1-segmented 35 



The 2 rami of each pair alike, but not combined as above 36 



The 2 rami in some pairs alike, in others different 38 



28. An extra segment attached as a median lobe to the posterior 



sinus of the genital segment; caudal rami horny, without setae 29 



No extra segment; caudal rami normal and armed with setae 30 



29. Second, third, and fourth segments each with dorso-lateral 



plates, the 3 pairs alike in form and position; no adhesion pads 



on thorax; fins of sharks 9 Parapandarus Wilson, 1924 (p. 439) 



Second segment with a pair of lateral plates, third and fourth 

 segments with dorsal plates, the 3 pairs unlike; 4 pairs of 

 adhesion pads; fins of sharks 9 Pandarus Leach, 1816 (p. 432) 



30. A single pair of dorsal plates on fourth thoracic segment 31 



Two pairs of dorsal plates, on third and fourth segments, 



latter covering urosome & Cecrops Leach, 1816 (p. 441) 



Two pairs of dorsal plates, second pair on genital segment 32 



Three pairs of dorsal plates, third pair on genital segment 34 



31. Second and third segments with 1 pair of lateral lobes; the plates 



on fourth segment fused at base; genital segment longer than 



wide; throat of sharks cf" 9 Nesippus Heller, 1865 (p. 438) 



Second and third segments separated, with 2 pairs of lateral 

 lobes; plates on fourth segment also separated; genital seg- 

 ment wider than long; gills of sharks 9 Prosaetes Wilson, 1907 



32. Dorsal plates on fourth segment covering less than one-third of 



genital segment; margins of carapace and plates smooth, 



without denticles; outside of fishes 9 Luetkenia Glaus, 1864 



Dorsal plates on fourth segment covering two-thirds of genital 



segment; margins of carapace and plates finely dentate 33 



