COPEPODS OF THE WOODS HOLE REGION 555 



129. Forehead with median spine, without a crest; endopods of 



fifth legs 1-segmented, right exopod 2-segmented, left 3- 



segmented, end segment spiniform; open ocean. 



cf Qaetanus Giesbrecht, 1888 (p. 50) 

 Forehead without spine but with crest; fifth endopods 1- 



segmented, right one clavate; exopods 3-segmented, left 



with a claw; open ocean cf Chirundina Giesbrecht, 1895 (p. 48) 



Forehead smooth, with neither spine nor crest 130 



130. Endopods of fifth legs 1-segmented, exopods 2-segmented; 



right leg the longer; exopod of second antenna 7-segmented 



and longer than endopod ; fresh water cf Senecella Juday , 1925 



Endopods of fifth legs 1-segmented; right exopod 2-segmented, 

 left 3-segmented; exopod of second antenna 6-segmented, 

 one-half longer than the endopod; open ocean. 



cT Drepanopus Brady, 1883 



131. Forehead with median spine; posterior corners of metasome 



with spines; first exopod 2- or 3-segmented, second endopod 

 1- or 2-segmented (fusion); open ocean. 



9 Gaetanus Giesbrecht, 1888 (p. 50) 

 Forehead without spine; first exopod always 3-segmented 132 



132. Posterior corners of metasome smoothly rounded 133 



Posterior corners of metasome produced into spines or points 137 



133. Exopod of second antenna 7-segmented, as long as endopod; 



rostrum lacking; maxillipeds enormously enlarged; urosome 



short and weak; open ocean 9 Pseudeuchaeta G. O. Sars, 1905 



Exopod of second antenna 6 or 7 segmented; maxillipeds of 



normal size 134 



134. Caudal rami as wide as long; second exopod segment of second 



antenna with only weak setae, or wholly without setae 135 



Caudal rami much longer than wide; second exopod segment 



of second antenna with 3 stout inner setae 136 



135. Exopod of second antenna 6-segmented, its second segment 



without setae; end spines of second, third, and fourth 

 exopods laminate, teeth coarse; littoral. 



9 Microcalanus G. O. Sars, 1901 

 Exopod of second antenna 7-segmented, its second segment 

 with setae; end spines of second, third, and fourth exopods 

 cylindrical, teeth fine (North Atlantic) 9 Bradyetes Farran, 1905 



136. Caudal rami half longer than wide, ciliated on inner margins; 



metasome three times as long as urosome; anal and preanal 



segments equal; fresh water 9 Senecella Juday, 1925 



Caudal rami twice as long as wide, without cilia; metasome not 

 twice as long as urosome; preanal segment much longer than 

 anal; open ocean 9 Pseudocalanus Boeck, 1872 (p. 43) 



137. Rami of second antennae subequal; posterior corners of meta- 



some extending backward beyond distal margin of the 



genital segment; bottom plankton 9 Undinopsis G. O. Sars, 1884 



Endopod of second antenna longer than exopod; fourth and 

 fifth metasome segments fused, their posterior corners 

 turned upward; bottom plankton 9 Comantenna Wilson, 1924 



Exopod of second antenna longer than endopod , , ,_ 138 



