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Show 286 MR. E. A. SMITH O N SHELLS FROM [Feb. 15, purplish dotted with brown, whitish at the suture and at Spire acutely conical, with rectilinear outlines. Whorls 7, flat, sloping, with a broad deep furrow at the lower part, which is margined above by a keel, which on the upper volutions is simple, remarkably prominent and acute, and giving to them quite a pagoda-like appearance. On the last two and a half whorls it is less acute and minutely nodulous; and above that there are three other granulous ridges, whereof the uppermost, or that immediately beneath the suture, is conspicuously the largest; these gradually become finer and less granulous as they ascend the spire, so that upon the first few whorls they are simple thread-like lirae; the last whorls also exhibit fine lirae of a similar character between the larger granulous keels, and the entire surface is ornamented with very fine lines of growth. The body-whorl is sharply angulated and carinate at the middle ; and the slightly convex base bears about eight principal concentric ridges with interlying finer threadlike ones. Aperture subquadrangular, within purplish at the upper part and whitish beneath, equalling about -^ of the entire length of the shell. Outer lip thin, obliquely receding, a little incurved above the carina, not thickened. Basal margin broadly sinuated, ex-curved, and slightly effuse. Columella thin, arcuate, a trifle reflexed at the umbilicus, and joined to the upper extremity of the labrum by a thin white callosity. Operculum horny brown, about 5-whorled, distinctly marked with arcuate lines of growth. Length 18 millims., diam. 11 ; aperture 7\ long, 6 broad. Hab. Lake Tanganyika {Thomson). I feel much pleasure in naming this species after Mr. Thomson, its discoverer. Among the several forms new to science contained in his collection this is perhaps the most remarkable. The colour of it is very difficult of description. The general tone of the spire is a sort of livid purplish tint, divided into zones by the whitish furrow which encircles the whorls immediately above the suture. The tubercles, too, upon the ridges also stand out in pale relief; and the interstices between them are frequently dotted with brown. The keel around the middle of the body-whorl is scarcely tuberculous, or at all events much less so than the carinae above. The base is almost entirely white, with the exception of red dotting sometimes present upon some of the larger ridges, which exhibit hardly any indication of tubercles. The effuse broad sinuation in the base of the aperture is best seen when the base of the shell confronts the eye. 22. LIMNOTROCHUS KIRKI. (Plate XXXIII. figs. 18-18 b.) Limnotrochus kirkii, Smith, Ann. & Mag. N. H. 1880, vi. p. 426. Shell solid, trochoid, dirty whitish, deeply and narrowly umbilicated. Spire acutely conical. Whorls 6 or 7, feebly concave, bearing arcuate and flexuous lines of growth and six or seven granulous lirae, whereof that immediately above the suture is the largest; body-whorl acutely angular at the periphery, encircled by two sub- |