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Show 262 MR. P. S. ABRAHAM ON THE [Mar. 6, Colour of the spirit specimens greyish white, clouded in parts; one example from Rodriguez, probably of the same species, is of a uniform dark grey. Length (in spirit) of a large specimen 75 millims., breadth 65. Hab. Mauritius ; Rodriguez. As in all the other species of Hexabranchus examined, there are apparently no mantle-spicules. The mouth is furnished with longitudinally-striated corneous lateral plates. The odontophore is large, with about 30 transverse rows of numerous lateral spines, which are large, upon elongated bases, and not so much recurved as in H. aneiteumensis. ACANTHODORIS MOLLICELLA, sp, nov. (Plate XXX. figs. 1-4.) Body ovate, convex, soft. Mantle covering the back and sides, but not extending over the border of the foot, bearing above large, long, linear or subcorneal, soft papillae, which are especially numerous at the sides and around the branchiae. Rhinophores long, slender, pointed, apparently conical and laminated far down ; the denticulated sheath, through which each is retractile, has two of the anterolateral divisions enlarged and produced into two long, flat, conical papillae. Branchiae 7 to 9, bipinnate, non-retractile, their bases united, and set in a star around the short tubular anal opening. Oral veil short from before backwards, with the lateral* ends free and flattened. Foot broad and oblong, truncated (or the outline curving inwards) in front, and without a transverse groove; it is flatly rounded behind ; and the border all round is flattened, crenulate, and extending beyond the mantle, particularly posteriorly. The colour of the spirit specimens is a uniform dark greyish olive. Length (in spirit) 28 millims., breadth 17, height 11. Hab. Lord Auckland's Islands. The mantle-spicules are comparatively few in number, small, spindle-shaped, and some rather bent. There is a very small spinous prehensile collar, between the laminae of which project two minute chitinous points (rudimentary lower jaw); its spines are very minute and recurved ; their shape could only be made out under a quarter-inch object glass. The odontophore is narrow and strap-shaped, and bears about 14 transverse rows of recurved spines ; the two median ones of each row are large, with more or less quadrangular elongated and laterally flattened bases ; outside these on each side are about 6 minute rudimentary spines. ACANTHODORIS GLOBOSA, sp. nov. (Plate XXX. figs. 5-9.) Body ovate, broad, very convex, and inflated. Mantle membranous on the back and sides, reaching down over the foot, except perhaps quite behind, and bearing scattered, soft, conical, pointed tubercles, which are more numerous towards the border. The rhinophores are apparently rather short and slender, laterally flattened and retractile within sheaths, of which two of the marginal denticulations are enlarged. Branchiae 7, bi- (? tri-) pinnate, non- |