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ShareA shell is a hard, rigid outer layer, which has evolved in a very wide variety of different animals, including mollusks, sea urchins, crustaceans, turtles and tortoises, armadillos, etc.
Scientific names for this type of structure include exoskeleton, test, carapace, and peltidium. The shells that are perhaps most familiar and most commonly encountered, both in the wild and for sale as decorative objects, are seashells, more precisely, the external shells of marine mollusks.
These are usually primarily composed of calcium carbonate, in the form of calcite or aragonite crystallised out in an organic matrix.
Calcium carbonate in mollusc shells can take different crystalline forms, one being nacre otherwise known as mother of pearl. Other kinds of animal shells are made from chitin, bone and cartilage, or silica.
For more information about the topic Animal shell, read the full article at Wikipedia.org, or see the following related articles:
Mollusca — The molluscs or mollusks are the large and diverse phylum Mollusca, which includes a variety of familiar creatures well-known for their decorative ... > read more
Gastropod shell — The gastropod shell is an animal shell which is part of the body of a gastropod or snail. It is an external skeleton or exoskeleton, which serves not ... > read more
Pearl — A pearl is a hard, rounded object produced by certain mollusks, primarily oysters. Pearl is valued as a gemstone and is cultivated or harvested for ... > read more
Snail — The name snail applies to most members of the molluscan class Gastropoda that have coiled shells. Other gastropods, which lack a conspicuous shell, ... > read more
Exoskeleton — An exoskeleton, in contrast to an endoskeleton, is an external anatomical feature that supports and protects an animal's body. All arthropods (such ... > read more
Scallop — Scallops are the family Pectinidae of bivalve molluscs. Like the true oysters they have a central adductor muscle, and thus their shells have a ... > read more
Skeleton — In biology, the skeleton or skeletal system is the biological system providing physical support in living organisms. Skeletal systems are commonly ... > read more
Oyster — The name oyster is used for a number of different groups of mollusks which grow for the most part in marine or brackish water. Inside a usually ... > read more
Cuttlefish — Cuttlefish are animals of the order Sepiida, and are marine cephalopods, small relatives of squids and nautilus. Cuttlefish have an internal shell, ... > read more
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