24 Bulletin Wisconsin Natural History Society [Vol. 13, No. 1 
differ in only two particulars from typical D. shoshone. These 
differences are in the length of the appendage on the antepenulti- 
mate segment of the right antenna of the male and in the form 
of the second basal segment of the right fifth foot of the male. 
In his material the antennal appendage is longer than the last 
two segments, but in the material from St. Paul Island the length 
of this appendage is subject to great variation, as shown in figure 
1, A-D. In some individuals it is only a little longer than the 
penultimate segment (fig. 1, A and C), as in typical D. shoshone , 
Fig. 1. Diaptomus shoshone var. wardi Pearse. A, B, C, D , Showing 
Terminal Process of Antepenultimate Segment of Male Right An- 
tenna. E, Showing the Second Segment of the Right Fifth Foot of 
Male. 
while in others it extends beyond the end of the last joint of 
the antenna (fig. 1, B). In view of this fact it appears that the 
length of this appendage has little or no specific value for this 
form; and it is opportune to suggest that this taxonomic feature 
may undergo similar variation in other species of Diaptomus. 
In the wardi form the inner margin of the second basal segment 
of the right male fifth foot bears a blunt process, while shoshone 
does not possess this process. This structure is present on the 
specimens from St. Paul Island (fig. 1, E). This single differ- 
