120 GEOL. AND NAT. HIST. SURVEY OF MINNESOTA. 
lum is also more elongate, but this is subject to considerable varia- 
tion. 
The armature of the feet, structure of antennz and most diagnostic 
points agree so fully that I hesitate to separate the two forms. In the 
description of C. diaphanus given in the first edition some of the state- 
ments apply to C. varicans or an allied form. The form of the recep- 
taculum figured on Plate R, Fig. 12, of that report may be compared 
with that of Plate VII, Fig. 3°, Crustacea of Alabama, to illustrate 
the range of variation. 
* Cyclops phaleratus Koch. 
PLATES XVII, Fias. 1-7; XVIII, Fies. 2-24; XIX Fie. 1; XXI, Fies. 6-10. 
Koch ’35; Fischer ’51 (canthocarpoides); Lilljeborg ’53 (canthocarpoides); Claus ’57 
and ’63 (canthocarpoides); Lubbock ’63 (canthocarpoides); Sars ’63; Fric ’72 (can- 
thocarpoides); Poggenpol ’74 (lascious); Uljanin ’75; Brady ’78 and ’91; Herrick 
82 (adolescens), and ’84 and ’87; Cragin ’83 (perarmatus); Daday ’85°; Richard 
791; Schmeil ’91 and ’92; Turner ’92; Marsh 793. 
Body sub-cylindrical, thorax little enlarged for the genus, abdomen 
large and cylindrical. The transition from thorax to abdomen is less 
sharply marked than usual. Cephalothorax oval, first segment longer 
than the remainder. Abdomen shorter than thorax, stylets short and 
profusely spinous. An oblique row of spines passes across the stylet 
some distance behind the lateral spine, which is very short, and other 
rows of spines or teeth may ornament the inner aspect or may be 
absent. The whole inner aspect is also ciliate. The outer apical seta 
is a ciliate or toothed spine and the inner is shorter and weaker. The 
outer median seta is nearly as long as the abdomen and is sparsely 
clothed with sharp teeth. The inner median seta is about half as long 
and similarly ornamented. The antenna is usually 10 jointed but fre- 
quently is 11-jointed, (?) and is much shorter than the first thoracic 
segment. The swimming feet all have three-jointed rami and are 
strongly armed with closely set short teeth. The armature of the ter- 
minal joints of the fourth foot is as follows: 
ex. 2 spines. ex. 1 seta. 
Outer ramus {2 1 spine, 1 seta. Inner ramus se 2 spines. 
in. 4 sete. Ins 2 Sete: 
Egg-sacs appressed, closely filled with many ova. I here append 
the original description of Cyclops adolescens Herrick (—C. perarmatus 
Cragin) for comparison with the description of C. affinis as transcribed 
below, as it contains other data: ‘‘Thorax oval, broad, acute ante- 
riorly; last segment large and separated by a constriction from the 
anterior ones. The head is beaked below; first thoracic segment large 
and long (0.36 mm.); last thoracic segment wide, united closely with 
the first abdominal segment, armed with series of teeth. Abdomen 
DS Bete A 
