Mopalia lignosa (Gould, 1846)

This three inch chiton has a medium wide girdle covered with thick recurved bristles. The mucro is slightly posterior and depressed. The sculpturing of the central area of valves and jugum is radiated pitting which is finer at dorsal and gets larger towards the girdle. The lateral area is flat and granular and appears nearly smooth. It is definable by a slightly raised rib. The color of the valves is slate blue streaked with dark brown. The color of the girdle is cream (shown on the left). The species ranges from Sitka, Alaska to Magdalena Bay, Baja California, Mexico.
The variation (Mopalia lignosa elevata Pilsbry, 1893),(shown on the right) which ranges from Alaska to Puget Sound, Washington, has a strong cream or white colored feathery pattern on the valves but is now in synonomy with Mopalia lignosa (Gould, 1846).