Sell disease on native oysters in Britain initially became established in Essex. It is now well established there and is present in natives in beds at Whitstable and in Cornwall. It has also been found in Clew Bay, Eire (unpublished report by C. Duggan to Irish Fisheries Department). Authors have suggested that oyster shell disease is caused by the presence of a fungus in the shell. No clear description of the organism can be traced.