426 Wisconsin Academy of Sciences, Arts, and Leiters. 



Length of female, 1.25 mm. Length of male, 1.15 mm. 



Li 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 

 hai5 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. Forbes 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 I>eardsley ('02) from 

 Seely lake, Colorado, and by Pearse ('05) from JJ'ebraska. 



DiAPTOMus MiNUTUs LiUjcborg. 

 Plate XVII, figs. 7, 11. Plate XVIII, figs. 1. 7. 



1889. Diaptotrus minutus DeGuerne and Richard (Lillj.), p. 



50; pL I, figs. 5, 6, 14; pi. Ill, fig. 25. 

 1891. Diaptomus mimdus Marsh, p. 212. 

 1893. Diaptomus minutus Mai-sh, p. 199 ; pi. IV, figs. 1-3. 

 1895. Diaptomus mimdus Marsh, p. 8; pi. VII, fig. 3. 

 1895. Diaptomus 'rninidus Llerrick and Turner, p. 59 ; pi. 



VIII, fig. 9. 

 1897. Diaptomus mimdus 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 tlie 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 



