ART. 14 NORTH AMERICAN COPEPODS MARSH 3 



11 (12). Fir.st .segment of right exopodite of male fifth foot with marlied quad- 



rangular hyaline ajipendage Diaptomus birgei Marsh, 1894. 



12 (11). Fir.st segment of right exopodite of male fifth foot with triangular pro- 



jection Diaptomus vireiniensis Marsh, 1915. 



13 (10). Antepenultimate segment of right antenna of male not produced into 



blunt point on distal end 14, 



14 (15). Inner process of the terminal segment of exopodite of left fifth foot of 



male falciform, no hyaline appendage on first segment of right exo- 

 podite Diaptomus pallidus Herrick. 1879. 



15 (14). Inner process of terminal segment of left cxopdite of male fifth foot 



digitiform 16. 



16 (17). Endopodites in both male and female fifth feet two-segmented, a hyaline 



process on second basal segment of right fifth foot of male. 



Diaptomus castor Jurlne, 1820. 



17 (16). Endopodites of both male and female fifth feet one-segmented, or in 



D. tyrelU the left endopodite of the male is sometimes indistinctly 

 two-segmented, a hyaline appendage on inner distal angle of first 

 segment of right exopodite of male fifth foot 18. 



18 (19). Lateral spine of second segment of right exopodite nearly straight; no 



blunt spine on posterior surface of this segment. 



Diaptomus tyrelli Poppe, 1888. 



19 (18). A second hyaline appendage on dorsal side of distal margin of first 



segment of right exopodite of male, lateral spine of second segment 

 of right exopodite strongly curved, and a blunt spine on the posterior 

 surface of this segment Diaptomus coloradensis Marsh, 1911. 



20 (1). Antepenultimate segment of right antenna of male with lateral lamella 



or terminal process 21. 



21 (30,52). Antei>enultimate segment of right antenna of male with hyaline 



lamella 22. 



22 (25). Hyaline lamella broad, extending beyond the end of the segment, sec- 



ond basal segment of right exopodite of male fifth foot armed on the 

 posterior surface with a small hook 23. 



23 (24). In male fifth foot the right endopodite is about one-half as long as the 



first segment of the exopodite, the left endopodite reaches about the 

 middle of the second segment of the exopodite ; in the female fifth 

 foot the exopodite is two-segmented, with two spines representing the 

 third segment ; the setae on the endopodites are of ordinary length. 



Diaptomus leptopus Forbes, 1882. 



24 (23). In male fifth foot the right endopodite about equals in length the first 



segment of the exopodite, the left endopodite nearly reaches the end 

 of the second segment of the expedite ; in female fifth foot tbe third 

 segment of the exopodite is indistinctly separated, two spines on the 

 third segment and one on the second, the setae of the endopodites are 

 unusually long Diaptomus piscinae Forbes, 1S93. 



25 (22). Hyaline lamella antepenultimate segment of right antenna of male nar- 



row, extending beyond the end of the segment slightly if at all — 26. 



26 (27). Second basal segment of right fifth foot of male armed with a hook 



equal in length to the first segment of the exopodite. 



Diaptomus clavipes Schacht, 1897. 



27 (26). Second basal segment of right fifth foot of male not armed with 



hook : — — 28. 



28 (29). First segment of exopodite of right fifth foot of male short and broad. 



Diaptomus gatunensis Marsh, 1913. 



