Operculum (gastropod)

The operculum is attached to the upper surface of the foot and in its most complete state, it serves as a sort of "trapdoor" to close the aperture of the shell when the soft parts of the animal are retracted.

However, some terrestrial pulmonate species are capable of secreting an epiphragm, a temporary structure that can in some cases serve some of the same functions as an operculum.

When these were first described they were thought to be valves of a bivalve species, then for many years after that they were considered to be a form of paired or single operculum-like structures belonging to ammonites.

[citation needed] In those marine species where the operculum completely seals the shell, it can also serve as a protection against predators when the snail body is retracted.

[citation needed] In life, the operculum is attached at the ending of the columellar muscle with an opercular disc dorsally to the upper surface of the posterior part of the foot.

The operculum, a cuticular development of these cells, is composed, as may be seen in the corneous opercula of Murex, Purpura, Triton, of very thin superimposed layers.

[citation needed] The oldest known human depiction of an operculum together with the shell of Charonia tritonis is a seal made by the Minoan civilization.

[3] Opercula of certain gastropods, especially varieties from the Red Sea, have long served as an incense material in ancient Jewish tradition, as well as Arabian cultures.

Incense producers in these countries use the operculum of many conches and other marine snails, including those found in Southeast Asia, South America, and East Africa.

[citation needed] Friedrich Ratzel in The History of Mankind[4] reported in 1896 that, in Oceania, chains and girdles composed of the coloured opercula of certain shells were considered valuable ornaments.