The phylum mollusca includes such species as clams, squid, octopuses, and snails. The Octopuss is really the only animal in the phylum without a shell of this type. Mollusks have coelomate bodies and a complete digestive track.
Mollusks are bilateraly symetrical and are protostomes.
A radula is tonugelike organ that all members of the phylem have, except for bivalves, who obtain their food by filter feeding. The radula can be protruded or moved by the animal. It is covered with a row of backward pointing teeth. Some members of this phylum use the radula for scraping algea or other food materials off of a substrate. Active predetors use the radula for puncturing their prey and sucking out the food.