Most molluscs are identified by the shape and pattern of their shell or shells. The shell protects them from predators.
This is a large group of animals that includes snails, slugs, mussels, octopuses and squids. Molluscs have two major features, or evolved from animals that had these features. These are a shell made from calcium and a muscular foot for moving. The first ancestors of octopuses and squids also had these features. Shells grow throughout the life of molluscs. The largest shells are grown by giant clams.