The periostracum is a thin, organic coating that is the outermost layer of the shell of many shelled animals, including molluscs and brachiopods. Among molluscs, it is primarily seen in snails and clams, i.e. in gastropods and bivalves, but it is also found in cephalopods such as Allonautilus scrobiculatus. The periostracum is an integral part of the shell, and it forms as the shell forms, along with the other shell layers. The periostracum is used to protect the organism from corrosion.
The gastropod shell is part of the body of a gastropod or snail, a kind of mollusc. The shell is an exoskeleton, which protects from predators, mechanical damage, and dehydration, but also serves for muscle attachment and calcium storage. Some gastropods appear shell-less (slugs) but may have a remnant within the mantle, or the shell is reduced such that the body cannot be retracted within (semi-slug). Some snails also possess an operculum that seals the opening of the shell, known as the aperture, which provides further protection. The study of mollusc shells is known as conchology. The biological study of gastropods, and other molluscs in general, is malacology. Shell morphology terms vary by species group.
Monoplex parthenopeus, common name the giant triton or giant hairy triton, is a species of sea snail, a marine gastropod mollusk in the family Cymatiidae. It preys on other molluscs.
Murex trapa, common name the rare-spined murex, is a species of sea snail, a marine gastropod mollusc of the family Muricidae, the rock snails.
Conus harlandi is a species of sea snail, a marine gastropod mollusk in the family Conidae, the cone snails and their allies.
Shutonia variabilis is a species of sea snail, a marine gastropod mollusk in the family Pseudomelatomidae, the turrids and allies.
Helicina rhodostoma is a species of tropical land snail with an operculum, a terrestrial gastropod mollusk in the family Helicinidae.
Peristernia is a genus of sea snails, marine gastropod mollusks in the subfamily Peristerniinae of the family Fasciolariidae, the spindle snails, the tulip snails and their allies.
Turbo tursicus is a species of sea snail, a marine gastropod mollusk in the family Turbinidae, the turban snails.
Coralliophila violacea, common name : the violet coral shell, is a species of sea snail, a marine gastropod mollusk in the family Muricidae, the murex snails or rock snails.
Drupa morum, common name the purple drupe, is a species of sea snail, a marine gastropod mollusk in the family Muricidae, the murex snails or rock snails.
Tenguella granulata, common name the mulberry shell or the granulated drupe, is a species of sea snail, a marine gastropod mollusk in the family Muricidae, the murex snails or rock snails.
Faunus ater is a species of brackish water snail with an operculum, an aquatic gastropod mollusk in the family Pachychilidae.
Conus denizi is a species of sea snail, a marine gastropod mollusk in the family Conidae, the cone snails, cone shells or cones.
Bayerotrochus tangaroanus, or Tangaroan slit shell, is a species of sea snail, a marine gastropod mollusc in the family Pleurotomariidae.
Bayerotrochus westralis, commonly known as "Australia's split shell", is a species of sea snail, a marine gastropod mollusk in the family Pleurotomariidae.
Syrnola violacea is a species of sea snail, a marine gastropod mollusk in the family Pyramidellidae, the pyrams and their allies.
Calliotrochus marmoreus is a species of sea snail, a marine gastropod mollusk in the family Trochidae, the top snails.
Conus aureopunctatus is a species of sea snail, a marine gastropod mollusk in the family Conidae, the cone snails, cone shells or cones.
Iotyrris notata is a species of sea snail, a marine gastropod mollusk in the family Turridae, the turrids.
