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Show 1 9 0 4 . ] ENTOMOSTRACA FROM NATAL. 127 This interesting species seems to occupy an intermediate position between Herpetocypris and Stenocypris so far as the antenna] setae, at least, are concerned, but from the shell-characters alone one would undoubtedly assign it to Stenocypris. Professor G. 0. Sars in his description of S. chevreuxii mentions the " partly denticulated " spines of the lobes of the first pair of maxillae, but does not figure them, and the antennal setae of that species are certainly much more fully developed both as to length and number than in S. perarmata. These points I have been able to confirm from an examination of British specimens of S. chevreuxii, which I have been fortunate enough to find in several localities :-very sparingly in a pond at Pike's Hill, and in the Hatchet Pond, both near Lyndhurst, and more recently in considerable quantity in ditches near the River Arun at Arundel, Sussex. Figures of the shell, antenna, and post-abdomen of S. chevreuxii are given in Plate VIII. figs. 5 8 - 6 2 . M a c r o th r ix a f f in i s , n . sp. (Plate VIII. figs. 6 3 -6 5 .) Body short, length about one-third greater than the breadth (fig. 6 3 ) . Head short and obtuse, with a rounded angle to which the antennules are attached ; dorsal margin gently arched, obscurely angulated at its junction with the posterior margin which is finely denticulated, ventral margin convex and fringed with rather long hairs: antennules (fig. 6 4 ) club-shaped, slightly dilated and truncated distally, crenulated on the outer margin which bears a few cilia, as also does the truncated extremity. Post-abdomen (fig. 6 5 ) spinulose along the whole of its posterior border and having a short terminal hooked claw. The antennae have the normal structure, not presenting any special characters, nor does the shell exhibit any definite ornament or sculpture. Length O'32 mm. This is a very small species, and is not very unlike the Northern M. laticornis, though only about half its size. E X P L AN A T IO N OF THE PLATES. P la t e V I . Cyclops gibsoni, $ > I>- 123. Fig. 1. Seen from above. Fig. 6. Posterior footjaw. 2. Antennule. 3. Mandible. 4. Maxilla. 5. Anterior footjaw. 7. Foot of first pair. 8. Foot of tbird pair. 9. Foot of fifth pair. 10. Furca. Cyclops pusillus, ? , p. 122. pig. 11. Seen from above. 12. Antennule. 13. Antenna. 14. Maxilla. Fig. 15. Anterior footjaw. 16. Posterior footjaw. 17. Foot of first pair. 18. Foot of fifth pair. Ectocyclops rubescens, $ , p. 124. Fig. 10. Seen from above. Fig. 20. Antennule. |