In bony fish, the gills lie in a branchial chamber covered by a bony operculum. Sclerites are not homologous to a gastropod operculum. This opening is hidden beneath a protective bony cover called an operculum. This opening is hidden beneath a protective bony cover called the operculum. Many species' eggs bear a fatty, knoblike capitulum that caps the operculum. They are sharply curved and with a clear convex operculum towards the narrower end. The deoxygenated water will eventually pass out through the operculum (gill cover). The Neritimorpha are a group of primitive "prosobranch" gilled snails which have a shelly operculum. The operculum and preopercle may or may not have spines. Mature buds are oval, long and wide with a rounded operculum. Within the orifice beneath the operculum there is a tongue-like lingula. A flap (operculum) opens and its stinging apparatus fires the barb into the prey. The aperture may have a lid (operculum), hence is described as operculate. Many, but not all sea snails have an operculum. Pericoronitis is an infection of the operculum of a partially impacted wisdom tooth.