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Cyclops phaleratus Koch was recorded in channel plankton only 
in small numbers in November—December, 1897, at minimum tem- 
peratures. E. B. Forbes (’97) states that it is a littoral form, 
confined to marginal vegetation. 
Cyclops prasimus Fischer.—Average number, 2. This species 
occurs sparingly and irregularly in September—March in channel 
plankton, appearing in largest numbers in the early autumn of 1895 
and most continuously in the winter of 1898-99. The numbers are 
always small, never reaching 400 per m.°%, and in 12 of the 17 records 
falling below 100 perm.’ The percentage of collections containing 
C. prasinus in the totals rises above 20 per cent. only in December 
(24 per cent.). The seasonal distribution in channel plankton 
indicates a limitation to the colder part of the year, all records but 
5 being below 40°. Nevertheless, in September—October, 1895, the 
species was recorded in 56°-79°. This fact and its relatively small 
numbers generally, make it probable that inferences from our 
scanty data concerning its seasonal distribution can not be con- 
clusive. 
Of the totals in all years, 86 per cent. are females without eggs, 
6 per cent. females with eggs (found in February and November), 
and 8 per cent. males. 
E. B. Forbes (’97) finds the species widely distributed in 
American waters from the Great Lakes to roadside pools. Marsh 
(93 and ’95) finds it (as C. fluviatilis) in the larger bodies of water 
in Wisconsin and Michigan, and in lakes Erie, Michigan, and St. 
Clair. In Green Lake he (’97) finds it to be the most abundant 
species of Cyclops, and perennial, with maxima in September— 
November. His statistical data exhibit somewhat irregular numbers 
which contain suggestions of recurrent pulses such as appear in 
our records of other species of Cyclops. Brewer (’98) finds the 
species in the plankton of pools near Lincoln, Neb. 
Cyclops serrulatus Fischer.—Average number, 3. This species 
was taken sparingly in channel plankton, exhibiting only isolated 
occurrences in December, January, March, and May, in flood waters 
at temperatures of 32°-75°. It is much more abundant in Spoon 
River, where it is sometimes the dominant species of the genus, 
appearing in May—September, and in small numbers in colder 
months. It appears to be adventitious in channel plankton of the 
Tllinois River. 
