As Sabellaria alveolata except middle row of opercular chaetae point distally, and outer ones tapered with long median tooth with several serrations on each side (S. spinulosa-opercular chaetae); (S. spinulosa-chaetae).
Up to 30 mm for 40 segments.
Made of cemented sand grains, often densely aggregated, their apertures forming a honeycomb pattern.
Wine-red, thorax with dark brown spots; tail light brown. Mature males whitish, mature females violet.
On rock or sand.
Eastern North Atlantic to Bay of Guinea, Black sea, North Sea to Kattegat.