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Show 292 MR. E. A. SMITH ON SHELLS FROM [Feb. 1 5, but differences of coloration and sculpture. M. tanganyicensis has the upper part of the whorls of the spire somewhat swollen and almost black, the lower half being light chestnut, the black portion beneath this in each whorl being concealed by the upper part of the succeeding volution. 34. M E L A N I A ( M E L A N E L L A ) NASSA, Woodward. (Plate X X X I V. figs. 26-26 6.) Melania (Melanella) nassa, Woodward, P. Z. S. 1859, p. 349, pi. 47, f. 1 ; Smith, P.Z.S. 1880, p. 348 ; Reeve, Con. Icon. fig. 216; Brot, Con.-Cab. pi. 6. f. 7. This Tanganyikan shell is subject to much variation, both in form and sculpture. The number of plicae in two of the specimens collected by Mr. Thomson is exceptionally small, there being but ten upon the last whorl. In contrast to this another example has twenty-six upon the same volution. One of the two former is also abnormal in another respect, namely in having the transverse ridges very narrow, thread-like, continuous on and between the plications, and of a brown colour. In the other they are whitish, interrupted by brown dots upon the lower part of the last whorl. The solid marine character of this species distinguishes it from all others, and when the operculum, at present unknown, and the animal are examined, it will probably receive distinct generic rank. Since writing the above, another series of this remarkable species has been sent to the Museum by Dr. Kirk of Zanzibar. Among this set are some exceptionally large specimens, peculiar also for a sub-truncation near the base of the columella. This I imagine would be concealed when the shell arrived at maturity by a deposition of callus. Although of very large size, not one of these appears to be adult, judging from the thickness of the outer lip. The number of transverse lirae on the last whorl is unusually large; and the whorls are broadly and flatly gradated. 35. MELANIA ( ?) HOREI. (Plate XXXIV. fig. 27.) Melania ( ?) horei, Smith, Annals & Mag. Nat. Hist. ser. 5, vol. vi. p. 427 (1880). Shell ovate-conical, smooth, brown, with a narrow white line beneath the suture. Spire conical, a trifle excentric, inclining very slightly to the right (the aperture being towards the eye and downwards). Whorls 6g, scarcely convex, exhibiting faint incremental striae. Suture simple; last whorl rising somewhat upon the preceding near the aperture, then suddenly descending to the margin of the labrum, furnished with a slight basal thickening, aperture ovate, rather acuminate above, purplish brown, occupying about |- of the entire length. Lip a little thickened, especially towards the suture, and somewhat patulate near the base. Columella whitish, moderately arcuate, united to the upper extremity of the labrum by a thin callosity. Length 14 millims., diam. 6^; aperture 6 long, 4 broad. Hab. Lake Tanganyika {Hore). |