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.
Most molluscs are identified by the shape and pattern of their shell or shells. The shell protects them from predators.
Many have a large muscular foot protruding from the shell that is used for slow movement. The muscles in the foot ripple, pushing the mollusc forwards. Other molluscs are protected in two shells and may be glued to a rock or coral and never need to move. Octopuses and squids have changed their foot into many flexible tentacles with suckers.
Some molluscs such as octopuses and squids have very intelligent brains and excellent eyesight.