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PKOCEEDINGS OF THE NATIONAL MUSEUM 



VOL. 75 



The descriptive notes which follow apply, of course, only to the 

 male. Length, 1.2 mm. The antennae do not quite reach the furca. 

 The furca is ciliated on the inner margins. The antepenultimate 

 segment of the right antenna has a slender, curved appendage which 

 slightly exceeds in length the penultimate segment, Figure 3. The 

 first basal segments of the fifth foot, Figure 4, have rather large 

 spines. The second basal segment of the right foot is quadrangular, 

 its length about twice its width. The first segment of the right 



exopodite is also quadrangular and 

 is about four-fifths as long as the 

 second basal segment; the second 

 segment is about twice as long as 

 the first, is strongly curved out- 

 wardly, and has the lateral spine 

 distad of the middle of the seg- 

 ment, while opposite the spine, 

 near the inner margin, there is a 

 small cuticular protuberance on the 

 posterior surface; the terminal 

 hook is symmetrically curved and 

 its length equals that of the exopo- 

 dite and second basal segment com- 

 bined. The right enclopodite is 

 broad, pointed, two-segmented, and 

 reaches the end of the first segment 

 of the exopodite. The left fifth 

 foot about reaches the end of the 

 first segment of the right exopo- 

 dite ; the terminal segment is setose 

 on the inner margin and bears two 

 digitate processes; the enclopodite 

 is slender, one-segmented, and is nearly as long as the two segments 

 of the exopodite. 



Figures 3-t.— 3, Diaptomus mexicanus, new 



SPECIES, TERMINAL SEGMENTS OF RIGHT AN- 

 TENNA OF male; X 607. 4, Diaptomus mexi- 

 canus, NEW SPECIES, FIFTH RIGHT FOOT OF 

 male; X 307 



DIAPTOMUS MINUTUS Lilljeborg, 1889 



Diaptomios mirmtios was described from collections made in Green- 

 land and at St. Johns, Newfoundland. DeGuerne and Richard, 1892, 

 reported it from Iceland. Marsh found it in many lakes in Wis- 

 consin and northern Michigan. It occurs in the Great Lakes, the 

 Finger Lakes of central New York, and in two localities in Maine. 

 It has been found at Dalhousie, New Brunswick, was reported by 

 Willey from the Shubenacadie River, Nova Scotia, and occurred in 

 collections made by Professor Mackay from Nipigon Lake. While 

 it is a very abundant species in the regions where it is found, it is, 

 so far as the continent of North America is concerned, somewhat 



