Subclass Amphineura is a taxonomic subgroup that includes a variety of marine organisms commonly known as chitons. Chitons are unique creatures with distinctive oval-shaped bodies and eight overlapping shells. This subclass is part of the larger phylum Mollusca, which also includes snails, clams, and squids. Other synonyms used for Subclass Amphineura include Polyplacophora, which refers to their many plates, and Chitonida, which is based on the common name of the group. The chitons' shells are made of aragonite, a form of calcium carbonate, and are often colored and patterned in intricate designs. Despite their tough exterior, chitons are preyed upon by a variety of marine creatures, including crabs, sea stars, and fish.