Snails belong to the phylum Mollusca. Molluscs are a diverse group of animals that includes snails, clams, mussels, octopuses, and squids. Molluscs have a soft body and often have a hard shell that protects their body. Snails have a distinctive spiral shell and a muscular foot that they use to move slowly along surfaces. The phylum Annelida includes segmented worms, such as earthworms, the phylum Echinodermata includes starfish, sea urchins, and other spiny-skinned animals, and the phylum Nematoda includes roundworms.