placophora

from The Century Dictionary.

• In Gegenbaur's system of classification, one of two primary divisions of the Mollusca, consisting of the chitons only.

from the GNU version of the Collaborative International Dictionary of English.

• noun plural (Zoöl.) A division of gastropod Mollusca, including the chitons. The back is covered by eight shelly plates. Called also Polyplacophora. See Illust. under chiton, and isopleura.