Distribution: Widespread in Atlantic and Pacific from arctic to tropical waters; uncommon; intertidal to 590 m in rock crevices (also reported from mangrove root mats and mud). The geographic range, range of climatic zones and variety of habitats may suggest that this is actually a species complex. Population genetic studies are desirable but may be difficult due to low abundance of individuals. Natural History Notes: Spawns in July and August (Gibbs, 1976). Characteristics: Smooth and slender body, up to 30 mm long, with short introvert and up to 36 digitiform tentacles. 8-10 rows of hooks on introvert. Photo scale bar: 5 mm.