Which mollusc group can be described as having several calcium carbonate plates along their dorsal side?

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Chitons, also known as Polyplacophora, have a shell made up of several calcium carbonate plates along their dorsal side, giving them a unique appearance. Cephalopods like squids and octopuses have a muscular mantle that encloses their body and bivalves like clams and mussels have two shells that are connected by a hinge. Gastropods like snails and slugs have a single, spiraled shell or no shell at all.

Which Mollusc Group Can Be Described as Having Several Calcium