Marstoniopsis scholtzi (A. Schmidt) and Ferrissia wautieri (Mirolli) from Hilgay, Norfolk.

The small hydrobiid prosobranch Marstoniopsis scholtzi (A. Schmidt) has hitherto been recorded in Britain only from canals in Lancashire and Cheshire and from timber ponds at Grangemouth in Stirlingshire. This restriction to artificial hahitats has led to the suggestion that it must have been introduced from the Continent, where it is widespread. A colony is now reported from the Great Ouse at Hilgay in Noffolk; also present at the same locality is the limpet Ferrissia wautieri (Mirolli), discovered in Britain in 1977 and, like Marstoniopsis, known otherwise from man-made habitats only. The history of the discovery of Marstoniopsis in this country is reviewed, together with data on fossil occurrences; the evidence for its native status remains ambiguous.