Cerion melanostomum Clench, 1934

Original Description

Shell cylindrical, rather solid, ribbed, and perforate. Color varying on individual specimens from flat white to mottled brown, first two whorls opaque and glasslike, remaining whorls porcelaneous. Interior of aperture a deep blackish brown. Whorls 10¾ to 11, first 7 whorls forming a fairly short and slightly convex cone. Remaining whorls about equal in diameter. Umbilical pit deep and sharply defined by a strong basal ridge which terminates at the base of the columella. Parietal tooth very well developed though not particularly long. This tooth is about twice as long as high. Columellar or axial lamella initiated high and well within the aperture, following back along the base of the columella to the whorl above as viewed in a sectioned specimen. There is a secondary parietal 'tooth' produced by the umbilical ridge. This is occassionally merged evenly with the parietal tooth, generally offset by a slight angle. In a sectioned specimen this ridge can be followed back to the fourth whorl, forming a canal around the axis. Aperture subquadrate, usually angled both above and below at the columellar margin. Lip entire, usually thinly ridged along the parietal wall and backfolded or collared, the collar descending unevenly, more so around the palatal margin and least developed over the umbilical pit.

Sculpture of strong but fairly close-set and somewhat irregular ribs, faintly indicated on the nuclear whorls. These number 32-36 on the body whorl. No smooth forms ocurred in a series of some 5000 specimens.

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