STATE GEOLOGIST. 145 



Antennae 17- jointed. 



I. — Fifth Foot 1- jointed. 

 Sp. 2. Cyclops ater, Herrick. 



(PJateQ^. Figs. 9— 12.) 



This is our most striking species and loves the clearer flowing 

 waters. The thorax is broadly oval and, usually, of a deep color. 

 Antennae as long as the cephalothorax (1.2 mm.), slender, and 



tapering toward the end; formula^ — :x-' ^ — -^^ ^._:::i^-. • 



last three joints rather short, the last joint furnished with an 

 unserrated knife-like ridge as in C. tenuicornis; maxillipedes 

 rather large; fifth foot one-jointed, armed with three subequal 

 spines; abdomen rather short, last segment especially short; 

 stylets of moderate length; setse rather short, internal seta much 

 longer than the outer, lateral seta near the end of the stylet; 

 eggs pale. Color deep blue or gray. Length 2.1 mm. The young 

 can be recognized without a glass by the band of deep color which 

 crosses the thorax in the middle. 



Collected near Minneapolis, in " Mud lake " and Bassett's creeks 

 This species has been collected in different parts of the Mississippi 

 valley from Alabama to Minnesota, but is nowhere very abundant^ 

 being but rather more so southwardly. 



II. — Fifth Foot 2-jointed. 

 A. — First joint o/Jifthfoot very broad. 



Sp. 3. Cyclops viridis, Jurine. [Rehberg.) 



(var. a.) 



C. vulgaris, koch, fischer, saks. 



C. hrevicornis, claus, lubbock, hellek, fric, hoek. 



C. viridis, cragin. 

 (var. b.) 



C. gigas, claus, sars, fbic, brady. 



C. ingens, herrick. 



The American form is usually somewhat different from the C. 

 gigas, but the stage prior to maturity is like that figured by Brady. 

 Observations made over a considerable territory and for a period of 

 several years led me to the conclusion expressed by Rehberg (Ab- 



1 The accent marks are userl to signify that joints represented by them (counting 

 from base) are either long—, short w or medium ii, 



10 



