1: gill plumes translucent grey-brown, but base of gills distinctly paler (sometimes darker) than the adjacent mantle. 2: black-brown tubercular processes within gill circle. 3: pale unpigmented tubercles appear as pale spots, often darkly outlined, when viewed from directly above. 4: rhinophores usually same as pale ground colour, but their widely-spaced lamellae are often dark-pigmented. Length 7.5 mm, Orkney, March 1976.