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 ...

Snails grow by gradually increasing the size of their shells in a spiraling pattern. As they consume calcium-rich food, they secrete calcium carbonate, which adds new layers to the shell’s edge.

"This geographic pattern suggests that selection has shaped ... has given way to more permanent evolution—the thicker snails' shells became fixed genetic traits over generations.

A tiny new species of snail with an unusual shell has been named after the painter Pablo Picasso. Researchers who discovered the three-millimetre creature say they came up with the name because ...