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Show 270 MR. E. A. SMITH ON THE [Apr. 1, Operculum calcarium, ex anfractibus duobus constitum, inferne Iceve, incrementi lineis striatum, extus porcis spiralibus septenis valde incequalibus, sulcis interjicientibus profundis, instructuin. (Plate X X I . fig. 14 a.) In style of coloration this species resembles Ar. tceniata, the well-known species from the Indian Ocean and the Philippines. It is, however, of a slightly different form, and the colour, both externally and within the aperture, is dissimilar. The two forms are at once distinguishable by the opercula. The operculum of N. tceniata (Plate XXI. fig. 15) is externally grooved and ridged, like that of N. turtoni, but the ridges are more numerous and more equal in size. The figures on Plate XXI. show at a glance the difference. The operculum of N. tceniata has not previously been described. The specimen figured was collected at Aden by the Rev. A. W . Baynham, who, in 1885, presented to the British Museum a very interesting series of shells from that locality. NATICA DILLWYNII, Pavraudeau. Hab. Mediterranean in many places ; Mauritius (Robillard); South Pacific Islands (B. B. Woodward). After carefully comparing Maltese specimens of this species with examples of the West-Indian N. proxima of C. B. Adams, I am quite convinced that they all belong to one and the same species. Philippi (see Kiister's Conch.-Cab. Monog. Natica, p. 123) holds them distinct, observing that N. proxima is more ovate in form, and that the umbilical ridge is much thicker and situated below the middle of the umbilicus. In answer to this, I would observe that these differences do not exist in specimens in the Cumingian Collection, sent by C. B. Adams himself. None of the St. Helena specimens are full-sized, but several are very brightly coloured. In the British Museum is a single specimen sent direct from the Mauritius by M . Robillard, which is absolutely identical with West- Indian examples with which I have compared it, and specimens from the South-Pacific Islands shown to me by Mr. Woodward seem to belong undoubtedly to this species. NATICA SANCT-E-HELEN^E. (Plate XXI. fig. 16.) Testa parva, umbilicata, ylobularis, nitida, albida, zona interrupta rufo-fusca infra suturam cincta, lineis pallidioiibus, ziczac-formibus, prope umbilicum saturatioribus, zonam indistinct am formantibus, ornata; anfractus 5, rapide accrescentes; spira parva, parum prominens ; umbilicus parvus, callo columellari albido semioblectus ; apertura semicircularis. Alt. 9 millim., diam. max. 9. This species probably attains a larger size than the above dimensions indicate. It resembles N. alderi of Forbes in form, excepting that the tip of the spire is scarcely so pointed, but the style of markings may be sufficiently different to distinguish it. Besides the rich brown, more or less interrupted zone beneath the suture, and the less distinct one around the umbilicus, the angles of the zigzag |