Ot eof GEOL. AND NAT. HIST. SURVEY OF MINNESOTA. 
slender, tapering toward the end; formula* —~-~——-~—_~-__=~~ 
——-—; last three segments not elongate, the last being furnished with 
an unserrated, hyaline knife-like ridge as in (. tenuicornis. Anten- 
nules much as in C. tenuicornis. 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 sete 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: 
tex. 2 spines. ex. 1 seta. 
Outer ramus | ap. 1spine, 1 seta. Inner ramus | ap. 2spines. 
in. 4 sete. in. 2 setz. 
The sete 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. 
PRATHER V; 
Subspecies europzeus 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’721 (C. brevicornis) ; 
UJjanin ’75; Hoek ’76 (C. brevicornis); Rehberg ’80!; Daday ’85°; 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 ’721 (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 ’82 and ’83 (C. ingens). 
If we accept Rehberg’s suggestion that the two European species, 
C. brevicornis and C. 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 Rehberg’s discovery of greater latitude of varia- 
* The characters in these formu’ 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. 
