COPEPODA 



759 



19 (18) Inner process of terminal segment of left exopodite of male fifth 



foot digitiform, hyaline appendage on internal distal angle 

 of first segment of right exopodite 20 



20 (21) Lateral spine of second segment of right exopodite nearly straight, 



no blunt spine on posterior surface of this segment. 



Diaptomus tyretti Poppe 1888. 



Widely spread in the mountain lakes of the West. 

 Length of female, 1.2 mm. 

 Length of male, 1.15 mm. 



FlG. 1181. Fifth feet of male Diaptomus tyretti. X 190. 

 (Original.) 



21 (20) A second hyaline appendage on dorsal side of distal margin of first 



segment of right exopodite, lateral spine of second segment 

 of right exopodite strongly curved, and a blunt spine on 

 posterior surface of this segment. 



Diaptomus color adensis Marsh 1911. 



In the Rocky Mountains in Colorado D. tyretti is replaced by this closely 

 allied species which is, apparently, the characteristic species of the moun- 

 tain lakes of Colorado. 



Length of female, 1.38 mm. 



Length of male, 1.32 mm. 



FIG. 1182. Fifth feet of male Diaptomus color adensis. Xiao. (Original.) 



22 (9) Antepenultimate segment of male right antenna with lateral lamella 

 or terminal process . 23 



23 (26, 42) Antepenultimate segment of right antenna of male with hyaline 

 lamella. , 2 4 



