560 BULLETIN 159, UNITED STATES NATIONAL MUSEUM 



175. Fifth legs lacking in female; in male both fifth legs biramose, 



endopods 1-segmented, right exopod 2-segmented, left 

 exopod with 3 segments; open ocean. _ cf 9 Valdiviella Steuer, 1904 

 Fifth legs uniramose in female, 3-segmented; left leg in male 

 biramose, exopod 3-segmented, endopod 1-segmented; 

 right leg uniramose, 3-segmented; open ocean. 



cT 9 Undinella G. O. Sars, 1900 



176. Fifth legs biramose in both sexes; in female exopods 3-seg- 



mented, endopods 2-segmented; in male rami of right leg 

 2-segmented, of left 3-segmented; fresh water (Tasmania). 



cf 9 Brunella G. W. Smith, 1909 

 Fifth legs biramose in female, rami 1-segmented, rudimentary; 

 exopods of third and fourth legs 2-segmented; rostrum 

 shaped like duck's bill; Antarctic plankton. 9 Pseudoothrix Brady, 1918 



177. Fifth legs lacking in female; exopods of first 4 pairs of legs 



2-segmented; first antenna 3-segmented; caudal rami 13 



times as long as wide; open ocean 9 Morrrionilla Giesbrecht, 1891 



Fifth legs lacking in female; both rami of first 4 pairs of legs 

 1-segmented, except fourth exopod, which is 2-segmented; 

 caudal rami very short; Antarctic plankton. 



9 Euchaetopsis Brady, 1918 



Fifth legs present in femle, uniramose and 4-segmented; basal seg- 

 ments of right and left legs in both sexes fused across the 

 midline 178 



Fifth legs present in female, uniramose and 2- or 3-segmented 179 



178. Fifth legs in male uniramose 4-segmented; second segment of 



left leg with curved inner process (endopod?); urosome 

 symmetrical in both sexes; salt and brackish water. 



cT 9 Heterocope G. O. Sars, 1863 

 Right leg in male 4-segmented, left 2-segmented, its end 

 segment lamelliform with 2 opposable claws; male urosome 

 with stout process on left side; fresh water. 



cf 9 Lamellipodia Schmeil, 1897 



179. Fifth legs in female 3-segmented, end segment sharply toothed; 



left fifth leg in male 3-segmented, right 2-segmented; male 

 urosome distorted to the right; fresh water. 



d' 9 Epischura Forbes, 1882 (p. 115) 

 Fifth legs in female 2-segmented, end segment with 2 short api- 

 cal spines; male unknown; second endopod with deep exca- 

 vation on inner margin; Antarctic plankton.. 9 Plagiop us Brady, 1918 



KEY TO THE GENERA OF THE SUBORDER HARPACTICOIDA 



(Again the swimming legs, especially the fifth pair, furnish the best distinctive 



characters) 



1. Endopod of fourth leg lacking or replaced by 1 or 2 setae 2 



Endopod of fourth leg made up of 1 segment 4 



Endopod of fourth leg made up of 2 segments 20 



Endopod of fourth leg made up of 3 segments (see 10) 74 



