from a website, i'd say they are bad:
Several species from the genus Mopalia can be found on beaches in the Puget Sound area. They are distinctive in having hairs or bristles sprouting from their girdles. Chitons from this genus are also unusual because while most chitons are strictly herbivores, the Mopalias consume animal materials including sponges, bryozoans, and hydroids in addition to algae.
Mopalia muscosa , the mossy chiton (pictured above), reaches a length of about 3-½ inches and the red-brown hairs sprouting from its girdle have a bristly texture. The valves (overlapping plates) are dull shades of brown, black-olive, or gray and may be overgrown by encrusting organisms or seaweed. This species is often found out in the open on rocks.