Figure

Terminology applied to specialised shell structures. a, apertural barriers (A, columella lamella; B, parietal denticles; C, outer palatal; D, inner palatal; E, basal lamellae); b, breathing canals with short, triangular flanges (arrows showing auricles and breathing canals); c, strongly flanged breathing canals (arrows showing anterior and posterior flanges); d, pegged operculum; e, circular spiral operculum with central nucleus; f, D-shaped concentric operculum with excentric nucleus; g, apertural sinus; h, crenulate impressed suture; i, straight, flat suture; j, simple lip with body whorl not descending; k, reflected lip with body whorl rapidly descending; l, whorls rapidly increasing with body whorl flared; m, whorls slowly increasing and multi-whorled; n, straight columella; o, sinuous columella.