STATE GEOLOGIST. 145 



Antennae 17- jointed. 



I. — Fifth Foot 1-jointed. 

 Sp. 2. Cyclops ater, Herrick. 



(Plate Q 2. 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 '^ — ^^ ^ — ^-^^^^^^ ► 



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; setge 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 creek. 



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 of fifth foot very broad. 



Sp. 3. Cyclops viriclis, Jurine. CRehberg.) 



(var, a.) 



C. vulgaris, koch, fischer, saks. 



C. brevicornis, claus, lubbock, heller, fric, hoek. 



C. viridis, cragin". 

 (var. b.) 



C. glgas, claus, sars, fric, 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 used to signify that joints represented by them (counting 

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



10 



