90 GEOL. AND NAT. HIST. SURVEY OF MINNESOTA. 



slender, tapering toward the end; formula*— :r— — ^-^^-^^rr:- 



; last three segments not elongate, the last being furnished with 



an unserrated, hyaline knife-like ridge as in C. fenuicornis. Anten- 

 nules much as in G. tennicornis. Maxillipedes rather large. Fifth 

 foot one-jointed, armed with three subequal spines. Abdomen very 

 short, especially the last segment. Stylets rather more than twice as 

 long as wide, the three inner set;e long and pectinate but none very 

 long, external seta short, lateral seta near the end of the stylet. 

 Fourth foot with the following armature of apical joints : 



Ifex. 2 spines. ( ex. 1 seta. 



ap. 1 spine, 1 seta. Inner ramus \ ap. 2 spines, 



in. 4 setre. i in. 2 selte. 



The sette are all short and stout. Color deep blue or gray; young 

 with a deep band of color crossing the thorax near the middle. 

 Ovisacs pale, rather small. Length 2.1 mm. This, our most char- 

 acteristic American species, is sparingly but widely distributed, at 

 least, throughout the Mississippi Valley. 



Cyclops viridis Jurine. 1820. 



Plate XIV. 



Subspecies europajus Herrick. 



Var. a.— Koch '35 (C. vulgaris) ; Fischer '51 ; Claus '57 and '63 (C. brevicornis) ; Sars '63; 

 Lubbock '63 (C. brevicornis); Heller '70 (C. brevicornis); Fric'72^ (C. brevicornis); 

 Uljanin '75; Hoek '76 (C. brevicornis); Rehberg'SQi; Daday '855; Vosseler '86; 

 Sostaric '88; Thallwitz '90; Lande '90; Schmeil '91 ; Richard '91; Schmeil '92. 



Var. b.— Claus '57 (C. gigas); Sars '63 (C. gigas); Fric 'Ti^ (C. gigas); Brady '78 (C. 

 gigas); Sostaric (C. viridis var. gigas); Rehberg '80^. 



Subspecies americanus Marsh. 



Var. a. — Cragin '83 (C. viridis); Herrick '83 (C. parcus) and '84 (C. brevicornis) 

 (passim); Marsh '93 (C. americanus); Turner '92 (C. viridis). 



Var. b. -Herrick '62 and '83 (C. ingeus). 



If we accept Eehberg's suggestion that the two European species, 

 G. brevicornis and G. gigas, are but forms of the same species, we are 

 driven to a somewhat anomalous arrangement of the synonomy, 

 though, when so arranged, it expresses a not unusual parallel devel- 

 opment of species on the two sides of the Atlantic. As the writer 

 stated in 1882, the American representatives of this species differ in 

 several minor points from the European and a new name was given. 

 Later, in deference to Eehberg's discovery of greater latitude of varia- 



•i The characters in these formu'ie are used to indicate the relative length of the joints, from base to 

 tip, as follows: -^, short; ^^, medium; — , long. 



fex. exterior; ap.^apical; in.=interior aspect. 



