426 Wisconsin Academy of Sciences, Arts, and Letters. 
Length of female, 1.25 mm. Length of male, 1.15 mm. 
In the material I have examined, the endopodites of the male 
fifth feet have more commonly been one-segmented. Only rarely 
have I found the endopodites of the female fifth feet two-seg¬ 
mented. 
The original description was from material collected by Dr. 
Porbes in Lake Michigan. It is a common limnetic species in 
all the Great Lakes. It occurs in Pine lake, Michigan, which 
has an almost direct connection with Lake Michigan. It occurs 
in Green lake, Wisconsin; in this lake it is a winter form. 
(Marsh, ? 97, p. 193. Marsh, ? 03, p. 23.) I have found it 
once in Tomahawk lake, Wisconsin, and Schacht reports that 
Dr. Porbes found it in Lake Michigamme, Michigan, and in 
Yellowstone park collections. In general, it may be said that 
it is pretty largely confined to the large, deep lakes. It has, thus 
far, never been found north or south of the Great Lakes, with 
the exception that it has been reported by Beardsley (’02) from 
Seely lake, Colorado, and by Pearse (’05) from Nebraska. 
diaptomus minutus Lilljeborg. 
Plate XVII, figs. 7, 11. Plate XVIII, figs. 1, 7. 
1889. Diaptomus minutus DeGuerne and Richard (Lillj.), p. 
50; pi. I, figs. 5, 6, 14; pi. Ill, fig. 25. 
1891. Diaptomus minutus Marsh, p. 212. 
1893. Diaptomus minutus Marsh, p. 199; pi. IV, figs. 1-3. 
1895. Diaptomus minutus Marsh, p. 8; pi. VII, fig. 3. 
1895. Diaptomus minutus Herrick and Turner, p. 59; pi. 
VIII, fig. 9. 
1897. Diaptomus minutus Schacht, p. 156; pi. XXX, figs. 5-8. 
Of small size. The greatest width of the cephalothorax is 
in front of the middle. The first segment equals fully one- 
half the length of the whole cephalothorax. The last segment 
has rounded lobes which are each armed with a minute spine. 
The first segment of the female abdomen is nearly as long as 
the rest of the abdomen. It is slightly dilated laterally at the 
