page_title: Seashell
section_title: Soft corals
hierarchical_section_title: Seashell / Other more atypical kinds / Soft corals
caption_attribution_description: English: Gorgonacea shadow photo by transillumination on an X-Ray film Français&#160;: Ombre photographique de Gorgone par transillumination sur film radiologique
context_page_description: A seashell or sea shell, also known simply as a shell, is a hard, protective outer layer created by an animal that lives in the sea. The shell is part of the body of the animal. Empty seashells are often found washed up on beaches by beachcombers. The shells are empty because the animal has died and the soft parts have been eaten by another animal or have decomposed.
  A seashell is usually the exoskeleton of an invertebrate, and is typically composed of calcium carbonate or chitin. Most shells that are found on beaches are the shells of marine mollusks, partly because these shells are usually made of calcium carbonate, and endure better than shells made of chitin.
  Apart from mollusk shells, other shells that can be found on beaches are those of barnacles, horseshoe crabs and brachiopods. Marine annelid worms in the family Serpulidae create shells which are tubes made of calcium carbonate cemented onto other surfaces. The shells of sea urchins are called "tests", and the moulted shells of crabs and lobsters are exuviae. While most seashells are external, some cephalopods have internal shells.
context_section_description: The skeletons of soft corals such as gorgonians, also known as sea fans and sea whips, commonly wash ashore in the tropics after storms.
caption: An x-ray photograph of a gorgonian
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