Marsh — North American Species of Diaptomus. 431 



and Koimd 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. 



diapto:mus siioshoke Forbes. 

 Plate XVIII, Hgs. 2-5. 



1893. Diaptomus shoslione Forbes, p. 251; pi. XLII, figs. 



23-25. 

 1895. Diaptomus shoslione Herrick and Turner, p. 01: pi. V, 



fig. 11. 

 1897. Diaptomus shoslione Schacht, p. Ill; pi. XXV^I, figs. 



1-3. 

 1904. Diaptomus shoslione 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 

 f ureal setae are very long, being more than tliree-fourths the 

 length of the abdomen exclusive of the furca. 



The antennae about equal in length the eephalothorax. 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 



