Mollusca, or Molluscs are invertebrate animals. It comprises 85,000 species of animals. It is the largest marine phylum. Molluscs account for 23% of all marine organisms. Some classes of molluscs include Bivalva, Cephalopoda, and Gastropoda. The word mollusc comes from the Latin word mollis, which means soft. The scientific study of molluscs is called Malacology. This is the Giant Pacific Octopus, the largest octopus in the world.