COPEPODS OF THE WOODS HOLE REGION 557 



148. Inner margin and posterior surface of first basipod of fourth 



leg smooth and naked, or with cilia only 149 



Inner margin and posterior surface of first basipod of fourth 



leg armed with teeth or coarse spines 151 



149. Exopod of first legs 1-segmented; forehead without a crest; 



rostrum lacking; endopod of second legs 1-segmented and 



short; body depressed; open ocean 9 Chiridiella G. 0. Sars, 1907 



Exopod of first legs 2-segmented; forehead with or without a 



crest 150 



150. Forehead with a crest; caudal rami with dense tufts of hairs 



on inner margins; endopod of second antenna with 11 apical 



setae; open ocean 9 Chirundina Giesbrecht, 1895 (p. 48) 



Forehead with or without a crest; caudal rami with ciliated 

 inner margins; endopod of second antenna with 14 apical 

 setae; open ocean 9 XJndeuchaeta Giesbrecht, 1888 (p. 60) 



151. Endopod of second antenna rudimentary, one-fourth as long 



as exopod or less; fourth and fifth metasome segments fused; 

 exopod of first legs 2-segmented; open ocean. 



9 Euchirella Giesbrecht, 1888 (p. 55) 

 Endopod of second antenna scarcely shorter than exopod; 

 fourth and fifth segments distinctly separated; exopod of 

 first legs 3-segmented; open ocean 9 Pseudochirella G. O. Sars, 1920 



152. Fifth metasome segment with its posterior corners mucronate 153 



Fifth metasome segment with rounded posterior corners, 



sometimes armed with tufts of fine hairs 154 



153. Right fifth leg lacking, left uniramose, 5-segmented, reaching 



caudal rami; rostrum lacking; urosome 5-segmented, with 



a short anal segment; open ocean cT Aetideus Brady, 1883 (p. 44) 



Both fifth legs present, biramose; endopods 1-segmented, right 

 exopod 2-segmented, left 3-segmented; rostrum present; 

 anal segment almost obsolete; open ocean. 



cf Qaidius Giesbrecht, 1895 (p 52.) 



154. Left fifth exopod ending in a complicated hand for grasping 



spermatophore; left endopod rudimentary, often lacking 155 



Left fifth exopod without a grasping hand; left endopod always 



present and well developed, making both legs biramose 156 



155. Spines on distal segments of second maxillae with a dense 



fringe of short spinules; corners of metasome asymmetrical, 



left the larger; open ocean d^ Paraeuchaeta A. Scott, 1909 (p 65) 



Spines on distal segments of second maxillae with long scat- 

 tered spinules; posterior corners of metasome symmetrical 

 and smooth; open ocean cf Euchaeta Philippi, 1843 (p. 62) 



156. End segment of right fifth exopod elongate-acuminate, some- 



what curved and regularly serrated on the concave margin; 

 left endopod long; open ocean__ cf Euchirella Giesbrecht, 1888 (p. 55) 

 End segment of right fifth exopod short, bluntly rounded, and 

 not toothed on its inner margin; left endopod relatively 

 shorter; open ocean cf XJndeuchaeta Giesbrecht, 1888 (p. 60) 



157. Endopod of first legs made up of 3 segments 158 



Endopod of first legs made up of 2 segments 164 



Endopod of first legs made up of 1 segment 174 



158. Head with one or two pairs of dorsal cuticular lenses and with 



a curved spine or hook on each lateral margin 159 



Head with neither dorsal lenses nor lateral spines 161 



71987—32 37 



