More than 70,000 animals belong to the Phylum Molluska. These animals are defined by hard outer shells which protect their soft bodies--those octopi and squid which no longer have outer shells have internal fragments of these shells. Mollusks can be found in a variety of habitats from trees to freshwater streams to tidal pools to ocean deeps. These size of these animals ranges from 1/10 inch to over 70 feet in length. They can weigh anywhere from 3/100,000 of an ounce to more than 500 pounds.
Clams, oysters, snails, chitons, octopi, and squid are all members of the Phylum Molluska.