AHT. 14 NORTH AMERICAN COPEPODS MARSH 5 



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

 process ._ 53. 



53 (58). Process equals or exceeds in length penultimate segment 54. 



54 (55). Process about equals in length last two segments, second basal segment 



of right fifth foot of male dilated on inner margin, endopodites of 

 fifth feet in both sexes indistinctly two-segmented. 



Diaptomus eiseni Lilljeborg, 1889. 



55 (54). Process slightly exceeds in length penultimate segment 56. 



56 (57). Appendage of antepenultimate segment of male antenna broad, in male 



fifth foot outline of second segment of right exopodite convex, with 

 lateral spine nearly terminal, terminal hook sinuate. 



Diaptomus franciscanus Lilljeborg, 1889. 



57 (56). Appendage of antepenultimate segment of male antenna slender, in 



male fifth foot outline of second segment of right exopodite biconcave, 

 lateral spine distad of center of segment, terminal hook symmetrical. 



Diaptomus mexicanus, new species. 



58 (53). Process shorter than penultimate segment 59. 



59(70,73). One or both terminal processes of last segment of left exopodite 



of male fifth foot distinctly falciform 60. 



60 (67). Right endopodite of fifth foot of male small, shorter than first seg- 



ment of exopodite 61. 



61 (64). In right fifth foot of male the terminal segment of the exopodite 



is slender and elongate ; the terminal hook is stout ; the endopodite 

 is rudimentary 62. 



62 (63). The lateral spine long and slender; the left endopodite is spatulate. 



Diaptomus spatulocrenatus Pearse, 1906. 



63 (62). Lateral spine stout; left endopodite long and slender. 



Diaptomus conipedatus Marsh, 1907. 



64 (61). Terminal segment of right exopodite of male is of usual proportions; 



the tenninal hook is not markedly broad ; the endopodite is dis- 

 tinct 65. 



65 (66). Left fifth foot of male reaches end of second basal segment of right 



foot, lateral spine of second segment of right exopodite at about two- 

 thirds its length Diaptomus sanguineus Forbes. 1876. 



66 (65). Left fifth foot of male exceeds second basal segment of right foot, 



lateral spine of second segment of exopodite nearly terminal, dorsal 

 process on fifth cephalothoracic segment of female. 



Diaptomus saltillinus Brewer, 1898. 



67 (60). Right endopodite of fifth foot 'of male distinctly longer than first seg- 



ment of exopodite 68. 



68 (69). First segment of right exopodite of male fifth foot has transverse ridge 



on the posterior surface, the lateral spine of the second segment is 

 about one-half as long as the segment, the first segment of the female 

 abdomen has a prominent swelling on the right side. 



Diaptomus asymmetricus Marsh. 1907. 



69 (68). First segment of right exopodite of male fifth foot has two curved 



processes on posterior side, the lateral spine of the second segment 

 equals or exceeds in length the segment, the fifth cephalothoracic 

 segment of the female is armed with two dorsal processes. 



Diaptomus dorsalis, Marsh, 1907. 



70 (59, 73). One of the terminal processes of the left exopodite of male is a 



straight or nearly straight sharp spine 71. 



