1088 Wisconsin Academy of Sciences, Arts, and Letters. 



1905. Cyclops albidus Pearse, p. 150, pi. XIV, figs. 11 and 13. 



1906. " distinetus Brady, p. 697. 



1909. " signatus var. annulicomis Byrnes, p. 10, p. IV, rigs. 1-6. 



1909. " virido-signatus Byrnes, p. 23, pi. IX, rigs. 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 f ureal 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 (PI. LXXVT, 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 f ureal rami are about twice as long as wide. The in- 

 ner margins of the f ureal 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 (PI. LXXVI, 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 be 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 be 

 rows of spinules on the fourth, fifth, sixth and seventh segments. 



