Family: Mopaliidae, Mopalid Chitons view all from this family

Description 1 1/2-3" (3.8-7.6 cm) long. Elongately ovate; uneroded valves grayish-brown. Crowded, fine beads arranged in diagonal and radiating lines on side areas. Girdle wide, black or brown, naked, leathery, covering more than half of valves, and encroaching deeply between valves.

Habitat On rocks, intertidally to just below low-tide line.

Range Alaska to Monterey, California, occasionally further south.

Discussion This is one of the chitons that is not especially sensitive to light and is found on exposed rocks, often among seaweeds, where it feeds on diatoms and other algae. The females lay greenish eggs in the summertime. The living animal's food is reddish to salmon-colored. The genus name honors Lady Katharine Douglas, who in 1815 sent the first specimens to England.