COPEPODS OF THE WOODS HOLE REGION 591 



70. End segment of second antenna with 4 subequal claws; first 



antennae 6-segmented; maxilliped in normal position, with a 

 stout apical claw; parasitic on Terebella.^ ? Terebellicola M. Sars, 1861 

 End segment of second antenna with 3 unequal claws; first 

 antenna 4-segmented; maxilliped turned forward, with 2 

 unequal apical setae and no claws; gills of fishes. 



9 Taeniacanthus Sumpf, 1871 



71. Fifth legs entirely lacking; body long, straight, club-shaped; 



urosome 4-segmented in female, 5-segmented in male; eye 



unusually large; in compound ascidians. 



cf 9 Ophthalmopachus Hesse, 1866 



Fifth leg made up of a single segment 72 



Fifth leg made up of 2 segments 73 



72. Fifth leg cylindrical, without setae; second antenna prehensile, 



with 4 apical claws; caudal rami seven times as long as wide, 



no setae; parasitic on gastropod 9 Panaietis Stebbing, 1900 



Fifth leg conical, with 1 seta; second antenna nonprehensile, 

 with 6 setae; caudal rami twice as long as wide and setose; 

 pelagic, at surface cf 9 Oithona Baird, 1843 (p. 311) 



73. Genital segment greatly enlarged, as wide as metasome; end 



segment of fifth leg eight times as long as wide, setose on 



both margins; in compound ascidian 9 Megasanoixus Hesse, 1871 



Genital segment not enlarged; fifth leg much shorter 74 



74. Head half the entire length; metasome segments with projecting 



corners; caudal rami as long as the last 2 abdominal segments; 



pelagic, at surface 9 Hyalopontius G. O. Sars, 1909 



Head shorter; metasome segments without projecting corners 75 



75. Head one-third the entire length; first antennae 6-segmented, 



basal segments fused, with flattened spines or setae; fifth 

 leg with 4 end setae; gills of fishes_ cf 9 Artacolax Wilson, 1908 (p. 383) 

 Head one-fourth the entire length; first antennae 12-segmented, 

 basal segments not fused, with normal setae; fifth leg with 3 

 apical setae; fresh water (China) cf 9 Limnoithona Burckhardt, 1913 



76. Body of cyclopoid form; swimming legs normally developed 



and none of them lacking 77 



Body cylindrical, spherical, or flattened; swimming legs re- 

 duced in size and sometimes rudimentary or lacking 79 



77. Fifth leg 1-segmented, rudimentary; first antenna 7-segmented; 



second antenna 5-segmented; rostrum anchor-shaped, with 

 3 spines, outer ones curved; pelagic, at surface. 



9 Pseudolichomolgus Thompson and Scott, 1898 

 Fifth leg 1-segmented, with 2 very unequal setae; a lateral seta 

 on each side of fifth segment; first antenna 11- or 12-segmented; 

 second antenna 4-segmented; fresh water. 



cf 9 Microcyclops Glaus, 1893 (p. 325) 

 Fifth legs made up of 2 distinct segments 78 



78. Fifth leg with a long apical seta and a very short lateral spine 



on the end segment; rami of swimming legs equal in length; 



fresh water c? 9 Cyclops (part) O. F. Miiller, 1776 (p. 322) 



Fifth leg with long apical and equally long lateral seta on end 

 segment; endopods of swimming legs longer than the exopods; 

 fresh water d^ 9 Mesocyclops (part) G. O. Sars, 1914 (p. 330) 



