Vacant shells in water
Centre: Breadth 3.5 mm, 5 spiral ridges on base.
Top left: Breadth 7 mm, 7 spiral ridges on base.
Bottom left: Breadth 12.25 mm, 8 spiral ridges on base. Large round white-bordered umbilicus (always present in Britain). Parietal lip reflected as a glaze onto body whorl. Most of interior of shell thickened by shiny silvery white layers of aragonite crystals (nacre). Nacre absent from border just within outer lip; coloured as exterior of shell.
Right: Breadth 16mm, 11 spiral ridges on base. White columellar lip adjoining umbilicus. Cotton wool behind operculum; about 50% would be darkened by dark body if shell occupied.