COPEPODS OF THE WOODS HOLE REGION 575 



119. First exopod 3-segmented, prehensile, endopod 2-segmented, 



natatory; each fifth leg 1 spiniform segment, with short 

 apical claw and 6 lateral setae; pelagic, surface tow. 



9 Parapeltidium A. Scott, 1909 

 First exopod 3-segmented, endopod 2-segmented, both nata- 

 tory; each fifth leg a rounded lamina, wider than long, with 

 6 marginal setae, but no claw; muddy bottom, shallow water. 



cf 9 Stenheliopsis G. O. Sars, 1906 

 First exopod 3-segmented, endopod 2-segmented, both pre- 

 hensile; each fifth leg a transverse plate, with 4 setae; rudi- 

 ments of sixth legs present; muddy bottom, shallow water. 



cf Stenhelia Boeck, 1864 (p. 228) 



120. Exopod of second antenna 1-segmented; terminal claw of 



second maxilla large and stout; fifth legs obsolete, each 

 replaced by' 2 or 3 small setae; pelagic, 50 fathoms. 



9 Metaphroso Brady, 1910 

 Exopod of second antenna 2-segmented; terminal claw of 

 second maxilla weak; each fifth leg replaced by a minute 

 pointed tubercle without setae; muddy bottom, shallow 

 water 9 Campella Wilson, 1924 



121. Exopod of first legs with 1 or 2 segments 122 



Exopod of first legs always with 3 segments 126 



122. Exopods of first legs definitely longer than endopods 123 



Endopods of first legs definitely longer than exopods 124 



123. Body not depressed; no lateral epimeral plates; second endo- 



pod and third exopod modified in male; no ciliated spines 

 on appendages; littoral, among algae. 



cf 9 Harpacticus Mikie Edwards, 1838 (p. 181) 

 Body strongly depressed; metasome and urosome with lateral 

 epimeral plates; ciliated spines on second antennae and 

 swimming legs; littoral, among algae. _ cf 9 Zaus Goodsir, 1845 (p. 190) 



124. Basal segment of first endopod longer than 2 distal segments 



combined 125 



Basal segment of first endopod much shorter; first exopod 

 1-segmented; end segment of fifth legs four to eight times 

 as long as wide, with 5 setae; pelagic, surface tow. 



cf 9 Clytemnestra Dana, 1847 (p. 292) 



125. Basal segment of first endopod much widened and flattened; 



distal segment with 2 apical spines; end segment, fifth leg, 

 shorter than basal expansion; littoral, tide pools. 



cf Pseudothalestris Brady, 1883 (p. 210) 

 Basal segment of first endopod not widened or flattened; distal 

 segment with 1 apical spine; end segment, fifth leg, longer 

 than basal expansion; littoral, among algae. 



9 Diarthrodes Thomson, 1883 



