24 COLD SPRING HARBOR MONOGRAPHS. VII. 



one on either side of the seta. The foot strongly suggests the 

 fifth foot of C. signatus, but the spines are much shorter. Among 

 the individuals of this group there was a great uniformity in the 

 armature of the fifth foot. Because of the combined characteristics 

 of the two types, ririclis and signatus, seen in this Cyclops, I have 

 designated it C. virido-signotns. 



The receptaculum seminis seems to consist of three broadly oval 

 masses tapering slightly posteriorly. 



In the male the characteristics of the female are repeated in the 

 armature of the swimming feet, in the fifth feet and in the stylets. 

 The first abdominal segment is almost circular in outline when 

 seen from above, so wide is it. In the young of the form, the pos- 

 terior margins of the abdominal segments are all very coarsely 

 serrated as is also the posterior margin of the fifth thoracic seg- 

 ment. 



In the young forms there is the usual correlation between the 

 ten- jointed antennas and the two- jointed condition of the rami as 

 has been noted for other Cyclops. 



Cyclops Piilchclhis (Herrick). (Plate X.) 



The form here identified as C. piilchclhis (Herrick) is a com- 

 paratively small Cyclops of marked transparency even when loaded 

 with ova, which it produces in great abundance. The color is a 

 delicate blue. This species was taken from a sphagnum sw^amp 

 together with C. virido-signatus, figured on Plate IX. 



The cephalo-thorax is noticeably pointed in front and is broadest 

 near its middle region. The abdomen is long and slender with 

 comparatively elongated caudal stylets that carry two long plumose 

 setae. The antenme reach about to the third thoracic segment and 

 contain seventeen segments. The basal segment is very long and 

 narrow and the last three segments grow progressively longer, as 

 Herrick pointed out. 



The receptaculum seminis appeared very sharply outlined in the 

 adult females (Fig. 3, Plate X.). It consists of a wide low arch 

 directed anteriorly and of a narrower and deeper arch directed 

 posteriorly. In the middle region the sac is constricted. The labrum 

 is edged with thirteen very small teeth. The swimming feet are 

 armed as follows: 



