6 PROCEEDINGS OF THE NATIONAL MUSEUM vol.75 



71 (72). In male fifth feet the lateral spine of the second segment of the right 



exopodite is short, one-third the length of the segment, the terminal 

 hook is broad and saber-like, the left endopodite is marked with 

 transverse striae; the endopodites of the female fifth feet are two- 

 segmented Diaptomus stagnalis Forbes, 1882. 



72 (71). In male fifth feet the lateral spine of the second segment of the right 



exopodite is long, equaling in length the two segments of the exo- 

 podite, the terminal hook is long and slender, the left endopodite is 

 not marked with transverse striae ; the endopodites of the female fifth 

 feet are one-segmented Diaptomus floridanus Marsh, 1926. 



73 (59, 70). Terminal processes of left exopodite of fifth feet of male are digiti- 



form 74. 



74 (78). The right endopodite of tlie male fifth foot equals or exceeds the first 



segment of the exopodite 75. 



75 (76,77). The endopodites of the fifth feet of male are one-segmented. 



Diaptomus novamexicanus Herrick, 1895. 

 76(75,77). In both male and female fifth feet the endopodites are two-seg- 

 mented. The exopodites of the female fifth feet are three-segmented. 



Diaptomus bakeri INIarsh, 1907. 

 77(75,76). In male fifth feet, right endopodite two-segmented, left one-seg- 

 mented, first segment of female abdomen has a digitiform process on 

 right distal border Diaptomus washingtonensis Marsh, 1907. 



78 (74). Right endopodite of male fifth foot shorter than first segment of exopo- 



dite 79. 



79 (80,83). In male fifth feet, second basal segment and first segment of ex- 



opodite of right foot without hyaline appendages, lateral spine of 

 second segment of exopodite nearer proxhnal end of segment. 



Diaptomus nudus IMarsh, 1904. 



80(79,83). In male fifth feet a hyaline appendage on first segment of right 



exopodite 81. 



81 (82). In male fifth feet a hyaline appendage on inner distal angle of first 



segment of right exopodite, right endopodite nearly equal in length 

 to first segment of exopodite, digitiform process on right distal mar- 

 gin of female abdomen Diaptomus signicauda Lilljeborg. 1889. 



82 (81). In male fifth feet a quadrangular hyaline appendage on inner distal 



half of first segment of right exopodite, right endopodite much shorter 

 than the first segment of the expedite. 



Diaptomus siciloides Lilljeborg, 1889. 



83 (79,80). In male fifth feet second ba'sal segment of right foot with one or 



hyaline appendages, an oblique ridge on the posterior surface of the 

 second .segment of the right exopodite 84. 



84 (85). In male fifth feet the lateral spine of the second segment of the right 



exopodite equals in length the segment, there is a dorsal process on 

 the fifth cephalothoracic segment of the female. 



Diaptomus albuc[uerquensis Herrick, 1895. 



85 (84). In male fifth feet the lateral spine of the second segment of the right 



exopodite equals in length one-half of the segment, there is no dorsal 

 process on the fifth cephalothoracic segment of the female. 



Diaptomus purpureus Marsjh, 1907. 



DIAPTOMUS ALBUQUERQUENSIS Herrick, 1895 



D. lehnierl Pearse 19(34 is D. all>uquerquer\sis of Herrick published 

 in 1895. I), dhuquerqyuemis Schacht 1897 is D. Horidanus Marsh. 



