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
An intertidal and shallow sublittoral estuarine species found under stones on mud or muddy sand in sheltered situations. It also lives amongst green and red seaweeds growing at the extreme low tide level. This species, described as new to science from the Helford estuary as recently as 1974 (Miller, 1986), is now known from several sites on the Irish coastline (Lough Ine, Co. Cork and Mulroy Bay, Co. Donegal), and on the south coast of Cornwall (the Helford and Falmouth estuaries). Very recently (2008) a sizeable population was recorded in the shallow sublittoral water at Turnaware Bar in the Fal Estuary. The Helford population, certainly the intertidal population, seems to have declined markedly in the past twenty or so years. There are also possible recent records, for which validation is awaited, of this species from Plymouth Sound, Portland (Dorset) and the Welsh coast. Elsewhere this species is recorded south to, and into, the Mediterranean.
The Helford site has been designated as a V.M.C.A. within the Fal-Helford marine SAC and this species was added to Schedule 5 of the Wildlife and Countryside Act (1981) in 1998.
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.