Marsh—North American Species of Diaptomus. 431 
and Round lake at Charlevoix, which are intimately connected 
with Lake Michigan. I have not found it in other localities, 
although Schacht reports it from Indiana, Michigan, Oregon, 
Idaho, Washington and Yellowstone park. 
DIAPTOMUS SHOSHONE Forbes. 
Plate XVIII, figs. 2-5. 
1893. Diaptomus shoshone Forbes, p. 251; pi. XLII, figs. 
23-25. 
1895. Diaptomus shoshone Herrick and Turner, p. 61; pi. V, 
fig. 11. 
1897. Diaptomus shoshone Schacht, p. 141; pi. XXVI, figs. 
1-3. 
1904. Diaptomus shoshone Marsh, p. 147; pi. XXX, fig. 3; 
pi. XXXI, figs. 1-3. 
Conspicuous because of its size, as it is larger than any other 
described American species except D. stagnalis Forbes. 
First cephalothoracic segment indistinctly divided. The first 
segment equals in length the four following. The last cephal¬ 
othoracic segment terminates in two minute lateral spines. 
The first abdominal segment of the female is somewhat shorter 
than the rest of the abdomen, and is strongly dilated laterally 
about midway of its length. The second segment is very short. 
The third segment is a little less than one-half the length of the 
first, and is slightly shorter than the furca. The branches of 
the furca are ciliate on both the inner and outer margins. The 
furcal setae are very long, being more than three-fourths the 
length of the abdomen exclusive of the furca. 
The antennae about equal in length the cephalothorax. The 
right antenna of the male is swollen anteriorly to the geniculat- 
ing joint, and bears upon the distal extremity of the antepenul¬ 
timate segment a straight process. This process extends to 
rather less than half the length of the ultimate segment. 
The first basal segments of the female fifth feet are armed 
