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Show 1890.] MARINE MOLLUSCA OF ST. HELENA. 267 superne suturam haud attingens; columella inferne triplicata, plica suprema minima, interdum subobsoleta. Longit. 2\ millim., lat. Ii. M. lavalliana of d'Orbigny, a common West-Indian species, appears to more closely resemble this than any other. That form is, however, a little more solid, hardly so narrow, and has four or more folds on the columella. MARGINELLA (VOLVARIA) ATOMUS. (Plate XXIII. fig. 12.) Testa minuta, pyriformi-ovata, alba, pellucida, Icevis ; spira obtu-sissima, vix elata ; apertura angusta; labrum paulo inflexum et incrassatum, superne suturce junctum, intus haud denticulatum ; columella quadriplicata, plica suprema minutissima. Longit. lg millim., lat. 1. This species might almost be regarded as a small form of the Australian M. angasi, from which it seems to differ chiefly in size. The columella of that species is not quite the same, however, being furnished with a few additional denticles or plicae at the upper part. CASSIS TESTICULUS, var. Hab. West Indies. The St. Helena form of this species is that named C. crumena by Bruguiere. From the series of specimens examined, I am inclined to think that it cannot be held distinct. It appears to exist on the eastern side of the Atlantic, and has not, I think, been recorded from the western parts. The typical form, however, cf C. testiculus is known from the West-African coast, and a specimen from that region was presented to the Museum by F. P. Marrat, Esq. TRITON TRITONIS (Linne). Hab. W . Indies, Mediterranean, N . Australia, Pacific Islands. A single specimen in a very worn and broken condition, and which, when perfect, must have been about twelve inches in length, is all that was found by Capt. Turton at St. Helena. Mr. Melliss "obtained two living specimens which came ashore at Lemon Valley." The species occurs also at the Canary and Cape de Verde Islands, and it is well known from the West-Indian region. T. seguenzce, Aradas and Benoit, is, in m y opinion, the Mediterranean variety of this species. TRITON OLEARIUM (Linne). Hab. New Zealand, Port Jackson, Japan, Tahiti, West Indies, Mediterranean, &c, &c. The distribution of this species is truly remarkable, and has been ably discussed by Lischke1. The specimens from St. Helena have the spiral ridges much more prominently nodose than usual, the varices are thicker, and the labrum not effuse, but very solid and strong as in T. aquatilis. In 1 Japan, Meeres-Conchyl. part i. p. 48. |
