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New Suit This crab is a crustacean. Crustaceans outgrow their shells from time to time. They grow a new shell as they grow bigger, leaving the old shell behind. This is called molting.

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Turtle Tops Turtle shells are covered with scales that grow tightly together. Sea turtles, like the one here, have flatter shells than land turtles so they can zoom through the water.

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Snail Shell A snail's shell grows bigger right along with the critter. Their shells are made of calcium carbonate. If they don't eat enough calcium, their shells may grow thin and crack.

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