The polychaete Stygocapitella subterranea is found in upper shore stable coarse substrata and can be regarded as semi-terrestrial. It is known from similar habitats in widely distributed locations of continental Europe. The first two British records, from upper shore damp grit, are summarized here: one site is adjacent to a tidal mudflat near Plymouth and the other site is on the tidal River Thames, London. The two areas have different salinity regimes but similar sediment characteristics, in agreement with published accounts of the species' habitat preferences. It is likely that the species will eventually be found throughout the British Isles and may have been recorded in unpublished data. However, the restricted habitat of S. subterranea and the potential threats suggest that some consideration be given to the conservation of the species.
