Marsh — North American Species of Diaptomus. 433 



case in mv specimens, and in this my observations agree with 

 those of Schacht. 



Length of female, 2. 02 mm. Length of male, 2.595 mm. 

 These are the figures of Forbes. In my specimens there was 

 more difference between the males and the females. The fe- 

 males of the Pike's Peak specimens averaged 2.9 mm., and the 

 males 2.495 mm. 



The original description of Forbes was from material col- 

 lected in Lake Shoshone. It occurs in many lakes in the Yel- 

 lowstone park region according to him. In material sent to me 

 by Professor H. B. Ward, it occurred in collections in Dead 

 lake, Mirror lake and Lake Rocks in the Pike's Peak region. 



The species is very striking because of its great size. It is 

 highly colored, the specimens from Dead lake showing very 

 deep blues and reds ; the cephalothorax was of a deep blue, 

 while the antennae, maxillipedes and abdomen were red. 



DIAPTOMUS WAKDI PcarSC. 



1905. D. y\'ardi Pearse, pp. 148-9; pL XIII, figs. 1-4. 



'*'A rather large sj^ecies, one-fourth to one-third as wide as 

 long. Cej)halothorax rather stout and broadest about the mid- 

 dle; all the segments distinct, the first longer than the second, 

 and these two together making about one-half the cephalothorax. 

 Lateral lobes of the last thoracic segment seen from above ob- 

 tuse posteriorly and armed with a minute spine at the inner 

 and outer angles. First abdominal segment shorter than the 

 remainder of the abdomen and broader than the following seg- 

 ments. Second segment of the abdomen much shorter than the 

 third. Furcal rami short, about one and one-half times longer 

 than broad, and ciliate on the inner margin in the male. (The 

 number of specimens of the female was so few that no satis- 

 factory examinations of the furca could be made.) 



"First pair of antennae reflexed extend about to the furca; 

 composed of twenty-five articles. Antepenultimate article of 

 right male antenna provided with a long, blunt process which 



surpasses the distal end of the ultimate article. 

 28— S. & A. 



