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 ...

"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.

Our special video series looks at some of the more unique shells at the Bailey-Matthews National Shell Museum on Sanibel, ...