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Beautiful seashells that are washed ashore on beaches by ocean waves have always fascinated human beings. Shells come in a wonderful array of shapes, sizes, and colors. Shells are actually made by marine creatures to serve as their homes. Seashells are, quite simply skeletons of mollusks. Mollusks are a class of water animals that have soft bodies and hard outer coverings called shells. Human beings carry their bony skeletons inside and wear their soft bodies on the outside, but mollusks do just the opposite.

Shells are very durable and outlive the soft-bodied animals that produce them. Shells may be univalve or bivalve. Univalve shells are made up of just one unit, whereas bivalve shells have two units or two halves. Snails have univalve shells, and oysters have bivalve shells. Shells protect the soft-bodied animals from rough surfaces that can harm their bodies and from predators.

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