BYRNES: CYCLOPS OF FRESH WATER. 39 



Fig. 2. The right outer ramus of the fourth swimming foot of Fig. I, show- 

 ing three segments. The three-jointed ramus is almost invariably correlated 

 with the eleven-jointed stage of the antennae. 



Fig. 3. A young form, showing the general proportions of the body when 

 there are ten segments in the antennre. The varietal characteristics, i. e., the 

 short second segment of the antennule and the fringe of hairs on the inner 

 margin of the caudal stylets are already present. 



Fig. 4. The right outer ramus of the fourth swimming foot of Fig. 3, 

 showing but two segments. The two-jointed ramus is almost invariably 

 correlated witli the ten- and nine-jointed stage of the antennas. 



Fig. 5. The rudimentary fifth foot of Fig. i, showing the characteristic, 

 short, basal segment of the variety signatus coronatus. 



PLATE IV. CYCLOPS SIGNATUS (Annulicornis). 

 Camera Drawings. Leitz. 



Fig. I. An outline of an adult female with seventeen segments in the 

 antennae, showing the general proportions of the body. The stylets are 

 without the inner fringe of hairs. The form is slightly distorted by pressure 

 but shows the general relation of parts. 



Fig. 2. The antennule of Fig. i, showing the elongated second segment, 

 characteristic of the variety annulicornis. 



Fig. 3. The last two segments of the antennas of Fig. i., showing the 

 hyaline knife edge. The distal half of the edge of the last segment is very 

 finely serrated. 



Fig. 4. The rami of the fourth pair of swimming feet of Fig. i. showing 

 the characteristic tuft of hairs in place of a seta on the inner surface of 

 the distal segment of the inner ramus 



Fig. 5. The rudimentary fifth foot of Fig. i, showing the elongated basal 

 Segment characteristic of the variety. 



Fig. 6. An outline of a young female of the same variety, having but 

 eleven segments in the antennas. Rami three-jointed. The fringe of hairs 

 on the inner surface of the stylets is wanting, as in the older forms of the 

 variety. 



PLATE V. CYCLOPS AMERICANUS. Marsh. 

 Camera Drawings. Leitz. 



Fig. I. An adult female drawn from the dorsal view, showing the general 

 proportions of the body. The loose articulation of the thoracic segments 

 appeared to be entirely normal and was not due to pressure. 



Fig. 2. The outer and inner rami of the fourth pair of swimming feet 

 of Fig. I. They show the" three characteristic spines on the outer margin 

 of the distal segment of the outer ramus and the characteristic seta on the 

 outer margin of the distal segment of the inner ramus. 



Fig. 3. The rudimentary fifth foot of Fig. i. 



