invertebrates that possess a soft, unsegmented body and live in aquatic or damp habitats. Many have an external, calcareous shell (although some do not). PhylumMolluscais the second-largest phylum of invertebrate animals after thearthropods (Arthropoda), and includes gastropods (e.g. snails and slugs),cephalopods (e.g. octopuses), andbivalves (e.g. clams).