1904.] ENTOMOSTRACA FllOM NATAL. 123 



Cyclops gibsoni, n. sp. (Plate YI. figs. 1-10.) 



Female. Seen clorsally the outline is slender, gradually taper- 

 ing from before backwards, greatest width equal to about one- 

 third of the length (fig. 1) ; the second segment as wide as the 

 cephalic segment, slightly produced and angulated posteriorly, 

 third segment narrower and scai-cely at all produced at the 

 angles, fourth segment again narrower and without produced 

 angles ; last thoracic segment about as wide as the fourth from 

 side to side, but much narrowed from before backward, its lateral 

 angles distinctly produced and bearing a brush of six or eight 

 rather long setas ; abdominal segments gTadually tapering back- 

 wards, the combined lengths of the second and third equal to that 

 of the fourth, first segment rather larger than the fourth ; caudal 

 stylets slender (fig. 10), nearly equal in length to the abdomen, 

 about five times as long as broad ; the innermost of the two 

 apical setse is the longer and is about equal in length to the entire 

 abdomen, outer setse somewhat shorter ; the subsidiary setse are 

 three in number, short, subequal, and arise from the apices of the 

 stylets ; on the side of each stylet not far from the distal end is a 

 single very minute seta ; the larger setfe are very finely plumose. 

 The antennules are twelve- jointed (fig. 2), slender, bearing- 

 numerous set£e, and reach backwards as far as to the fi'ont of 

 the second segment : the proportionate lengths of the joints are 

 indicated in the following formula : — 



1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 

 3 li 1 2 H 1 2 4 3 3 31 4. 



The mandible is of the usual form, with a rudimentary palp of 

 three setse, two long and one short (fig. 3) ; the chewing portion 

 of the maxilla (fig. 4) is of normal shape, with a laminar palp bearing 

 several plumose setse. The rami of the first four pairs of feet ai-e 

 all three-jointed ; terminal joint of the outer branch of the first 

 pair bearing two slender spines on the outer margin, three long 

 setpe on the inner margin and two shorter apical setse, the outer- 

 most being fi.nely bipectinate (fig. 7) ; the terminal joint of the 

 inner branch has one long apical spine and on its outer margin one 

 very short spine and one slender seta, its internal margin has 

 three setse and one at the apex. The second, third, and fouith 

 pairs (fig. 8) are nearly similar, but with more elongated joints and 

 more robust spinous armature. The fifth pair (fig. 9) is uniarti- 

 culate, with three subequal setse, the innermost of which is densely 

 plumose. Length 1 mm. 



Among European species those most nearly allied to C. gibsoni 

 seem to be G. varicans, C. hicolor G. O. Sai'S and G. gracilis 

 Lilljeborg ; but all of these have the rami of the swimming-feet 

 uniformly biarticulate, whereas in G. gibsoni they are triarticulate. 



Cyclops fimbriatus Fischer, 



This appears to be one of the commonest species in Mr. Gibson's 



