Bathymophila callomphala

(Original description by M. Schepman) The polished, nacreous shell has a depressed-conical, shape. It has a thin, pellucid, white, external layer and often a yellow line below the suture. It contains 4 to 5 whorls. The nucleus is smooth, the subsequent 2 whorls are microscopically spirally striate, crossed by weaker growth-striae. The last 2½ whorls are smooth, with only very faint, traces of growth-striae and spiral striae, but with a row of oval beads, just below the conspicuous suture. The periphery is rounded. The base of the shell is nearly flat, impressed near the centre, which is more or less filled by a thick callus, which is white, with radiating striae on its external margin, granular near the columellar margin, and is ornamented there, with 4 or 5 granules. The base of the shell round the callus, is likewise provided with radiating grooves. The aperture is subtriangularly rounded, very oblique. The outer margin is thin, slightly thickened interiorly. The columellar margin is thickened, its upper end pressed to the body whorl, with a thin layer connecting the margins. The yellow operculum is externally concave. The shell varies in altitude, in the presence or absence of the yellow subsutural line and especially in the characters of the umbilicus, which is either closed, or more or less open. …