All mollusks build their own shells, whether they live in water or on land. Creatures like snails, clams, oysters and mussels use an organ called a mantle to secrete layers of calcium carbonate, which ...

Wander through your backyard or walk along a stream and it’s likely you’ll see a snail – small, squishy animals with shells on their backs. Snails are found in water, whether in salty oceans, rivers ...