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Show 96 SIR C. ELIOT ON NUDIBRANCHS [May 17, bears eleven pairs of branchiae, tlie main axis of which is bifiil and the secondary axis bifid again. The first pair of branchiae are set at the side of the rhinophores, which appear not to be on the dorsal margin, but this arrangement may be due to the contraction of the anterior part of the animal. The velum bears eleven simple processes of irregular length; the outermost are tentacular and grooved as usual. The jaws bear a single row of very large, bent, almost hamate denticles with slight indications of a second row. The radula consists of 36 rows, with a maximum formula of 27 + 1.1.1 + 27, but in most rows it is only about 15 + 1.1.1 + 15. The central tooth is broad, and, as in M. rcimosa, seems to bear five cusps. The stomach is provided with the usual girdle of about 100 triangular plates, all of much the same size. This form appears referable with tolerable certainty to M. arborescens B. M a r io n ia r am o sa , sp. n. One specimen dredged in 5 fathoms, north of Kokotoni, Zanzibar. The notes on the living animal are as follows:-" Colour cocoalike. Two rows of big branched processes which are greenish in their finer divisions. The rhinophores and processes of the velum very long. The neck part is long and the whole creature has the shape of Limax. Length about 2| inches." The preserved specimen is of a uniform light yellowish green, much bent, but about 27 millimetres long if stretched out. The back is only 8 mm. across, but the whole animal looks much broader on account of the large branchiae. These are thirteen in number, set on the somewhat projecting dorsal margin. The first are a little behind the rhinophores and the last at the end of the tail. None are rudimentary, and the longest are 11 mm. long and almost ribbon-like. The largest tufts consist of three main stems, each of which is trifid again. The velum is ample and bears, in addition to two tentacles of the usual grooved shape, twelve simple digitate processes. The largest are 2 mm. long; the four in the centre are much smaller than the others. The sides and back are tuberculate. The rhinopliore sheaths are 5-5 mm. high, with simple but ample and spreading margins. The club is surrounded by five plumes, once or twice pinnate. The jaws are not very strong, and, except that the cutting-edge is yellow, colourless. Both bear about thirty large pyramidal denticles, at the base of each of which is a small accessory denticle. In parts there are traces of a second line, which might be regarded as mere ridges on the first line of denticles, but which in seven or eight cases seem to be independent formations. The transparent radula consists of 45 rows, containing at most 29 laterals, so that the formula is 45x29 + l.l.l+ 2 9 a s a maximum. The central tooth is much as in Bergh's plates of Marionia arborescens (S. E. Heft xvii. pi. lxxxviii. fig. 34), and, as |