ENTOMOSTRACA OF MINNESOTA. 91 



tion than once supposed, G. ingens was united with G. gigas as an un- 

 named variety of G. virldis (Herrick'84, p. 145). The preimago stage 

 is similar to that of gigas, and this fact made the union seem more 

 legitimate. Still later Marsh, without recognizing the varietal differ- 

 ences and having only the smaller form before him, erects for it a new 

 species, G. americanus. Of course, if this is to include the whole 

 assemblage representing G. vlridis in America, the name G. ingens is 

 prior. If not, the later name may be revived for the form correspond- 

 ing to G. gigas of Europe. 



To judge from the figures in Claus' l>as Genus Gijclops, the European 

 form is subject to a very wide range of variation, for G. furcifer, after- 

 wards regarded as a simple varietal form of G. hrevicaudatus, has the 

 stylets and antennte greatly elongated. Unfortunately the details of 

 the armature of the feet are not given by Claus or most of the authors 

 following him. 



Var. a. * Cyclops americanus Marsh. 



Plate XIV. 



Subspecies Americanus Marsh. 



We quote Marsh's description entire: 



" Cephalothorax oval, the first segment being about half its total 

 length. Antenna? 17-jointed, about as long as the first cephalathoracic 

 segment. Abdomen rather slender, the last segment armed on its 

 posterior border with small spines. All the abdominal segments in 

 immature individuals are strongly pectirate posteriorly. Fiirca 

 about three times as long as its average breadth, the lateral spine sit- 

 uated well towards the end. The first and fourth terminal sette are 

 short, slender and plumose, nearly equal in length. Of the internal 

 setffi, the outer is a little more than three-fourths of the length of the 

 inner. The armature of the terminal joints of the swimming feet is 

 as follows: 



First Foot. 



!ex. 3 spines. ( ex. 1 seta, 



ap. 2 seta;. Inner ramus < ap. 1 spine, 1 seta, 



in. 2 selaj. (in. 3 seise. 



Second and Third Feet. 



!ex. 3 spines. (ex. 1 seta, 



ap. 1 spine, 1 seta. Inner ramus < ap. 1 spine, 1 seta, 



in. 3 se1a\ (in. 3 setse. 



Fourth Foot. 



!ex. 3 spines. C ex. 1 seta, 



ap. 1 spine, 1 seta. Inner ramus -I ap. 2 spines, 



in. 3 setaj. (in. 2 se1a3. 



"Fifth foot two-jointed, basal joint very broad, armed with one 

 seta. Terminal joint armed with a seta and a blunt spine. Length 

 1.2 mm." 



