Barnacles live only in the sea. They are related to crabs and lobsters.
Barnacles stick themselves to a surface and live there in the same place for their entire adult lives. You usually see them on the beach stuck to rocks, or stuck to the bottom of boats. They eat small sea creatures that drift past them in the water.
Scientific name: caracal caracal
A circle is a shape with one long, curved edge that is the same size in all directions. Things that are like a circle are often called round. The circle in this picture is a pot, with a cat asleep in it.
Scientific name: family: cardiidae
Cockles are related to clams, mussels and snails. They have a shell in two parts joined by a hinge. Cockles burrow into sandy beaches and eat tiny creatures in the water that washes over them.
Cockles can be caught and eaten. They are cooked in much the same way as other similar creatures like mussels.