4 PROCEEDINGS OF THE NATION" AL MUSEUM vol.75 



29 (28). First segment of exopodite of right fifth foot of male elongate. 



Diaptomus leoninicollinus Marsh, 1913. 



30 (21,52). Antepenultimate segment of right antenna of male bears a slender 



straight process 31. 



31 (36,43). Process much shorter than the penultimate segment 32. 



32 (35). Right endopodite of male fifth foot rudimentary 33. 



33 (34). Lateral spine of second segment of right exopodite of male fifth foot 



terminal Diaptomus lintoni Forbes, 1893. 



34 (33). Lateral spine of second segment of right exopodite of male fifth foot 



nearer the proximal end of the segment. 



Diaptomus trybomi Lilljeborg, 1889. 



35 (32). Right endopodite of male fifth foot about equal in length to the first 



segment of the exopodite; lateral spine of second segment of the 

 exopodite located near the center of the segment. First segment of 

 the female abdomen has a process extending backward from the 

 posterior margin of the right side Diaptomus judayi Marsh, 1907. 



36 (31,43). Process nearly or fully equals penultimate segment 37. 



37 (38). Right endopodite of male fifth foot equals in length first segment of 



exopodite, spines of first basal segments large. 



Diaptomus tenuicaudatus Marsh, 1907. 



38 (37). Right endopodite of male fifth foot exceeds length of first segment 



of exopodite, spines of first basal segments small 39. 



39 (40). Endopodites of male fifth feet two segmented. 



Diaptomus arcticus Marsh, 1920. 



40 (39). Endopodites of male fifth feet one segmented 41. 



41 (42). Inner process of terminal segment of left fifth foot of male falciform. 



Diaptomus bacillifer Kolbel, 1884. 



42 (41). Inner process of terminal segment of left fifth foot of male digitate. 



Diaptomus sicilis Forbes, 1882. 



43 (31,36). Process exceeds in length penultimate segment 44. 



44 (49). Lateral spine of second segment of exopodite of right fifth foot of male 



terminal or nearly so, antennae reach proximal end of furca 45. 



45 (46). Process of antepenultimate segment of right antenna of male only 



slightly longer than penultimate segment, antennae equal in length to 



cephalothorax Diaptomus shoshone Forbes, 1893. 



46(45). Antennal process of male exceeds ultimate segment, antennae reach 

 furca 47. 



47 (48). Endopodites of male fifth clavate, a small tooth about midway of 



inner border of second segment of the exopodites of the female fifth 

 feet Diaptomus augustaensis Turner, 1910. 



48 (47). Endopodites of male fifth feet slender and straight, no tooth on inner 



border of second segment of exopodite of female fifth foot. 



Diaptomus wardi Pearse, 1905. 



49 (44). Lateral spine of second segment of riglit exopodite of male fifth foot on 



proximal half of segment, antennae reach beyond furca 50. 



50 (51). Lateral spine of second segment of right exopodite of male fifth foot 



short, right endopodite rudimentary, endopodites of female fifth feet 

 rudimentary Diaptomus minutus Lilljeborg, 1889. 



51 (50). Lateral spine of second segment of right exopodite of male fifth foot 



long, right endopodite equals in length first segment of exopodite. 



Diaptomus ashlandi Marsh, 1893. 



