The periostracum is a thin organic coating or "skin" which 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.
Leiostyla lamellosa is an extinct species of small air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Lauriidae.
Cryptosaccus asturiensis is a species of air-breathing land snails, terrestrial pulmonate gastropod mollusks in the family Hygromiidae, the hairy snails and their allies. This species is endemic to Spain.
Partula taeniata, common name the Moorean viviparous tree snail, is a species of terrestrial gastropod in the Partulidae family. It is endemic to French Polynesia.
Trochulus biconicus is a species of air-breathing land snail, a pulmonate gastropod mollusk in the family Hygromiidae, the hairy snails and their allies.
Trochulus is a genus of small air-breathing land snails, terrestrial pulmonate gastropod mollusks in the subfamily subfamily Trochulininae of the family Hygromiidae, the hairy snails and their allies.
Trochulus graminicola is a species of small, air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Hygromiidae, the hairy snails and their allies. This species is endemic to Germany.
Noricella oreinos is a species of small, air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Hygromiidae, the hairy snails and their allies. This species is endemic to Austria.
Partula is a genus of air-breathing tropical land snails, terrestrial pulmonate gastropod mollusks in the family Partulidae. Many species of Partula are known under the general common names "Polynesian tree snail" and "Moorean viviparous tree snail". Partulids are distributed across 5,000 sq mi (13,000 km2) of Pacific Ocean islands, from the Society Islands to New Guinea.
Trochulus villosulus is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Hygromiidae, the hairy snails and their allies.
Plicuteria lubomirski is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Hygromiidae, the hairy snails and their allies.
Trochulus striolatus, previously known as Trichia striolata, common name the "strawberry snail," is a species of small, air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Hygromiidae.
Conus trochulus is a species of sea snail, a marine gastropod mollusk in the family Conidae, the cone snails and their relatives.
Caseolus calvus is a species of small air-breathing land snail, terrestrial pulmonate gastropod mollusks in the family Hygromiidae, the hairy snails and their allies.
Trochulus alpicola is a species of air-breathing land snail, a pulmonate gastropod mollusk in the family Hygromiidae, the hairy snails and their allies.
