Key facts

Length up to 15 cm, width up to 3 mm. Body somewhat dorsoventrally flattened, usually dark reddish brown with a paler dorsal side and somewhat irregularly interspersed thin, pale cross-bands. Head paler than body (sometimes entirely white, or at least with pale margins) with a row of up to 12 dark eyes on either side, and distinct lateral slits. Young juveniles are paler, eyeless and often lacking pale cross-bands. Typically found on shell gravel bottoms and among algae etc. on rock and stones from the shoreline down to a depth of 140 m or more, often in association with oysters. Occasionally found also on soft bottoms. Preys mainly on bristleworms of the family Polynoidae, but also known to catch closely related nemerteans.