Polyplacophora is a class of the phylum Mollusca (the molluscs) which includes of the chitons or coat-of-mail shells. The body of these primitive molluscs is covered by eight shell plates (called valves), articulated, so that it can bend, and held together by a muscular band or girdle round the edge of the body. The mouth and the anus lie at opposite ends of a bilaterally symmetrical body, and there are no eyes or tentacles. Chitons live crawling slowly about on rocks.