Identity:

This variant is typically found encrusting the upper faces of exposed and moderately exposed circalittoral rock and mixed substrata, subject to strong and moderately strong currents and high turbidity levels. The crusts formed by the sandy tubes of the polychaete worm Sabellaria spinulosa may completely cover the rock, binding gravel and pebbles together. A diverse fauna may be found attached to this crust, and in many cases reflects the character of nearby biotopes. There is normally considerable variation in the associated fauna encountered. There may be a sparse bryozoan turf (Flustra foliacea, Alcyonidium diaphanum, Bicellariella ciliata, Bugula plumosa and Vesicularia spinosa) attached to the Sabellaria crust and available rocky substrata. Other scour-tolerant species such as Urticina felina are occasionally observed. Clumps of robust hydroids such as Tubularia indivisa, Nemertesia antennina, Hydrallmania falcata and Halecium halecinum may also be observed. Other species which may be present include the polychaete Pomatoceros triqueter, Balanus crenatus, Asterias rubens, Pagurus bernhardus and Gibbula cineraria. Occasionally, sponges such as Haliclona oculata and Halichondria panicea, and ascidians such as Dendrodoa grossularia may also be observed.