Gastropod shell

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. An excellent source for terminology of the gastropod shell is 'How to Know the Eastern Land Snails' by John B. Burch now freely available at the Hathi Trust Digital Library.Upper image: Dorsal view, showing whorls and apexCentral image: Lateral view showing the profile of the shellLower image: Basal view showing umbilicus in the centre.Apertural view of shell of Valvata sinceraAbapertural view of shell of Valvata sinceraUmbilical view of shell of Valvata sinceraThis dorsal view of the living animal Calliostoma bairdii also shows an apical view of its shelloblong shell of Bulgarica denticulataglobose shell of Sphincterochila candidissimadepressed shell of Escargot de Quimpercap shapeear shapeneritiformplanispiraldepressed trochiform or valvatiformtrochiformovate-conicconicelongate-conic or turriform or cockscrew shapetop shapespindle shape – the sea snail Syrinx aruanus has the largest shell of any living gastropod.club shapeegg shapeirregular shapeTurritella communis, many-whorled shell of tower snailX-ray image of TurritellaShell of marine cowry snail – Cypraea nebritesHelix pomatiaEpitonium scalare spiral shellX-ray image of CypraeaX-ray image of the shell of Tonna galeaCharoniaMurex pectenThin section in plane-polarized light of microscopic gastropod shell, from Holocene lagoonal sediment of Rice Bay, San Salvador Island, Bahamas. Scale bar 500 µm. 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. An excellent source for terminology of the gastropod shell is 'How to Know the Eastern Land Snails' by John B. Burch now freely available at the Hathi Trust Digital Library. The gastropod shell has three major layers secreted by the mantle. The calcareous central layer, tracum, is typically made of calcium carbonate precipitated into an organic matrix known as conchiolin. The outermost layer is the periostracum which is resistant to abrasion and provides most shell coloration. The body of the snail contacts the innermost smooth layer that may be composed of mother-of-pearl or shell nacre, a dense horizontally packed form of conchiolin, which is layered upon the periostracum as the snail grows.