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“Margarites gemma, n. sp. Pl. I, fig. 1.
Shell turbinate, moderately umbilicated, thin, greenish-iridescent, finely spirally lirate throughout, the threads upon the base below the periphery finer than those above, sculptured also with fine arcuate lines of growth, which are coarser towards the suture, giving a somewhat cancellated appearance to the shell at this part; they cross the four or five spirals below the narrowly channeled suture, producing minute sharp points or nodules upon them; whorls 5½, the nucleus globose, white, smooth, porcellanous; the next whorl with four spirals; the third with seven, not all equal in thickness; the penultimate with eleven; and the last having about fourteen above the periphery and about twenty-five below; the umbilical area is smooth, dirty white; peristome thin, subcircular, interrupted on its junction with the whorl, the columellar margin slightly thickened, expanded upon the whorl and very narrowly reflexed; aperture iridescent and finely sulcate, the grooves corresponding to the external liræ. Greater diameter 22, smaller diameter 19, height 18 mm.
Station 194, off Oates Land, 180-200 fathoms.
Only a single specimen of this beautiful shell was obtained. M. charopus, Watson,* from Kerguelen Island, is an allied form, but differs in colour and details of sculpture.
* “Challenger” Gasteropoda, p. 78, pl. V, figs. 6-6B.”
(Smith, 1915: 62-63)