1088 Wisconsin Academy of Sciences, Arts, and Letters. 
1905. Cyclops albidus Pearse, p. 150, pi. XIV, figs. 11 and 13. 
1906. “ distinctus Brady, p. 697. 
1909. “ signatus var. annulicornis Byrnes, p. 10, p. IV, figs. 1-6. 
1909. “ mrido-signatus Byrnes, p. 23, pi. IX, figs. 1-8. 
A rather large species. The cephalothorax is oval in form, 
but the tapering at the posterior end is not so pronounced as 
in some species. The length and breadth compare as about 
5 to 3. The cephalothorax is a little more than twice as long 
as the abdomen exclusive of the furcal rami. The projection 
of the posterior angles of the segments is not very marked. 
The dorsal surface of the fifth segment is more or less clearly 
marked with four rows of small spines. 
The first abdominal segment (PL LXXVI, fig. 5) is not 
markedly larger at its anterior end; this first segment is some¬ 
what longer than the sum of the three following. The last ab¬ 
dominal segment has a row of spines on its posterior margin. 
The furcal rami are about twice as long as wide. The in¬ 
ner margins of the furcal rami are not usually armed with 
cilia; sometimes, however, they are present. I have found 
this condition in specimens collected in Michigan and in some 
collected in Colorado. The lateral seta is situated near the 
end of the furca. Of the four apical setae, the outer is very 
short, not much exceeding in length the ramus; the inner 
is about three times the length of the outer. 
The first antennae are composed of seventeen segments, and 
reach about the full length of the cephalothorax. The last 
three segments (PL LXXYI, fig. 8) bear a hyaline plate, which 
in the last segment may be finely serrate on the margin. In oc¬ 
casional specimens this hyaline plate may he seen in some 
of the preceding segments, and in exceptional cases may be 
traced the whole length of the antenna, being represented in 
most of the segments by a row of small spines. Occasionally, 
too, the eighth, ninth, tenth, twelfth, thirteenth and fourteenth 
segments may have a row of spines on the posterior border as 
in C. fuscus. The twelfth segment has a long seta and a club- 
shaped sensory seta. The first two segments may have ir¬ 
regular rows of spines. In exceptional cases, there may he 
rows of spinules on the fourth, fifth, sixth and seventh segments. 
