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Show 1 9 0 4 . ] ENTOMOSTRACA FROM NATAL. 1 2 3 C yclops g ib so n i, n. sp. (Plate VI. figs. 1- 10.) Female. Seen dorsally the outline is slender, gradually tapering 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 scarcely 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 setae ; abdominal segments gradually tapering backwards, 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 setae is the longer and is about equal in length to the entire abdomen, outer setae somewhat shorter; the subsidiary setae 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 setae are very finely plumose. The antennules are twelve-jointed (fig. 2), slender, bearing numerous setae, and reach backwards as far as to the front 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 1 * 1 2 1 * 1 2 4 3 3 4. The mandible is of the usual form, with a rudimentary palp of three setae, 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 setae. The rami of the first four pairs of feet are all three-jointed; terminal joint of the outer branch of the first pair bearing two slender spines on the outer margin, three long sette on the inner margin and two shorter apical setae, the outermost being finely 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 setee and one at the apex. The second, third, and fourth 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 setae, the innermost of which is densely plumose. Length 1 mm. Among European species those most nearly allied to C. gibsoni seem to be C. varicans, C. bicolor G. 0. Sars and C. gracilis Lilljeborg; but all of these have the rami of the swimming-feet uniformly biarticulate, whereas in G. gibsoni they are triarticulate. C yclops fim b r ia tu s Fischer. This appears to be one of the commonest species in Mr. Gibson's |