SECRETS of the SHELLS

Walking along the beach, you spot a shell. It’s beautiful—spiraled and pointy, with a dotted brown-and-white pattern. And here’s one that looks like a ribbed pink-and-white fan. And this one is long like a ruler. Who made all these shells? And how? And why? Shells on the beach were all grown by living sea animals. Their hard homes are not just pretty. They also help the animals survive. Sea worms and sand dollars created some of them.

Others were once homes of crabs. But most of the shells that wash up on beaches were made by mollusks.

The Shell-Makers

Hard ocean shells are made by different kinds of soft-bodied animals.

Crustaceans

Lobsters, crabs, and barnacles grow hard exoskeletons.

Echinoderms

A flat, round sand dollar is the internal shell of a sea urchin.

Worms

Some marine worms construct hard