The descriptive text, below the map, is from the Cornish Red Data Book (2009). The map on this web page depicts the organisms distribution and shows the records made pre-2000 and those made since.
Habitat & Distribution
Found on rocky sea-shores at around the mid-tide level, apparently preferring pools where the dominant algal cover is that of the red alga Corallina officinalis and various encrusting Lithothamnion species. A Mediterranean species, it is at the most northern extremity of its range in south-west Britain from Dorset to Pembrokeshire, and south-west Ireland. It is also recorded further north on the west coast of Britain in north-west Wales, the Outer Hebrides and the north-west coast of Ireland. It is probably most common in the southwestern half of Cornwall where, in places, it may be described as being quite frequent.
I.J. Bennallick, S. Board, C.N. French, P.A. Gainey, C. Neil, R. Parslow, A. Spalding and P.E. Tompsett. eds. 2009. Red Data Book for Cornwall and the Isles of Scilly. 2nd Edition.Croceago Press.
The Cornish Red Data Book Project was led by the Cornwall and Isles of Scilly Federation for Biological Recorders (CISFBR). The full text and species accounts (minus the maps) are available on the CISFBR website.