Shellfish is a family of animals that include:
Limpet is a common name applied to a group of sea snails, marine gastropod molluscs which have a simple broadly conical shell that, unlike the shell of most snails, is not coiled.
Cephalopods (squid and octopus) belong to moluscs as well.
Crabs, lobsters, crayfish, shrimp, krill and barnacles.
Starfish, sea urchin, sand dollars, seabiscuits, sea cucumbers.