Mastonia crassula (Martens, 1880)

Original description. 

Testa ventricosa, conico-ovata, granulis supra suturam biseriatis, fusconigricans, apice pallide flavescente; anfr. circa 6, sat celeriter crescents, ultimus angustus, basi liris circa 3 granosis cinctus, apertura parva, simplice. Long. 2½, diam. 1⅓, apert. ⅔ mm. Mauritius, im Sand, Prof. Möbius. Der obere Gürtel ist öfters heller gefärbt, aschgrau. Obgleich nur unvollkommene Exemplare vorliegen, so ist der Gesammthabitus doch so eigenthümlich, dass ich ihnen einen Artnamen nicht versagen wollte. Nächstverwandt sind Trif. pupaeformis Desh. moll. de Reunion pl. 12, fig. 3, 4, welche durch die helle Färbung und die ungekörnte Basis sich unterscheidet, und T. atomus Issel malacologia del mar rosso pl. 4, Fig. 4, p. 280 fossil und noch kleiner, 1½ mm lang, ¾ breit.

Translation of original description.

Inflated shell, ovate cone shaped, with two series of tubercles above the suture, deep brown with apex light yellowish; approximately 6 whorls, which grow fast, the last whorl is smaller, the base has 3 tubercled spiral cords, the aperture is small and simple. Length 2½ mm, diameter 1⅓ mm, aperture ⅔ mm. Mauritius, in sand, Prof. Möbius. The first thread is often light ash-grey of colour. Although, only imperfect specimens are present, the overall look of the specimens are so unusual, that I could not leave them without a name. Related species are T. pupaeformis Desh. (Moll. de Reunion pl. 12, fig. 3, 4), which is distinguishable by its light colouring and base without tubercles, and T. atomus Issel (Malacologia del Mar Rosso pl. 4, fig. 4, p. 280) which is a fossil species and even smaller, 1½ mm in length and ¾ in width.

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