COPEPODS OP THE WOODS HOLE KEGION 541 



9. Fifth legs with 3-segmented exopods and 2-segmented endopods, 



third exopod segment attached to center of second segment; 

 exopod of second antenna with 2 segments; pearl-oyster wash- 

 ings 9 Ridgewayia Thompson and Scott, 1903 



Fifth legs with 2-segmented exopods, highly modified, and 1- 

 segmented endopods; exopod of second antenna longer than 

 endopod and made up of 7 segments (Suez Canal). d^Suezia Gurney, 1927 



Rami of fifth legs 3-segmented in both sexes and like the other 



legs 10 



Rami of fifth legs unlike in two sexes and uialike the other legs 11 



10. First basipod with hook and spine on anterior surface; basipod 



of fifth leg not denticulate; left fifth exopod prehensile in 



male; pelagic cf ? Canthocalanus A. Scott, 1909 



First basipod without hook or spine; inner margin of fifth basi- 

 pod denticulate; left fifth exopod in male natatory, not pre- 

 hensile; pelagic d^ ? Calanus Leach, 1819 (p. 19) 



First basipod without hook or spine; inner margin of fifth basi- 

 pods serrate; fifth legs natator.y in female, prehensile and 

 asymmetrical in male; pelagic cf ? Nannocalanus Sars, 1925 



11. Middle segment of second exopod often invaginated; right 



fifth leg in male biramose, very short; left leg long, uniramose 



or biramose; pelagic, at surface cf 9 Undinula A. Scott, 1909 (p. 29) 



Middle segment of second exopod not invaginated; both 

 fifth legs in male very long, exopods 3-segmented, right 

 endopod 3-segmented, the left 1-segmented; pelagic, at surface. 



cf 9 Calanoides Brady, 1883 



12. Fifth legs uniramose in female, 3- or 4-segmented; biramose in 



male, endopod rudimentary or lacking, exopod 2- or 3-seg- 

 mented, right one uncinate; fresh water. 



c?" 9 Pseudodiaptomus Herrick 1884 (p. 101) 

 Fifth legs uniramose in both sexes, 2-segmented in female, api- 

 cal segment lamellar, 5-segmented in male, apical segment 

 a slender, curved, smooth claw (Indian Ocean). 



cf 9 Metacalanus Cleve, 1901 

 Fifth legs different from above 13 



13. Caudal rami five to seven times as long as wide 14 



Caudal rami only three times as long as wide, or less 16 



14. Fifth legs biramose, rami 3-segmented, symmetrical in female, 



asymmetrical in male; fourth basipod in female with sword- 

 like spine; fresh water (Australia) cf 9 Gladioferens Henry, 1919 



Fifth legs in male biramose, asymmetrical, in female uniramose, 

 symmetrical, 3-segmented, middle segment with inner spine 

 and large process; brackish and salt water, cf 9 Poppella Richard, 1888 



Endopods of fifth legs 3-segmented in both sexes; exopods in 

 females 3-segmented, middle segment with inner spine, in 

 male 2-segmented, asymmetrical 15 



15. Inner exopod spine of female fifth legs smooth; second basipod 



of right fifth leg of male with smooth margin; end claw of 

 right exopod short; plankton of Great Lakes. 



d^ 9 Limnocalanus G. O. Sars, 1863 

 Inner exopod spine of female fifth legs with 2 rows of teeth; 

 right fifth basipod of male with long process, end claw long 



and slender; fresh water (Asia) cf 9 Sinocalanus Burckhardt, 1913 



71937—32 45 



