MolluscIreland - land and freshwater
  • Pisidium milium Held 1836 Rosy or quadrangular pea mussel

Map hosted by the National Biodiversity Data Centre, Waterford
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A tumid, roughly rectangular shell with broad, swollen umbos lying behind the mid point. Surface very glossy, with fairly strong, irregular, concentric striae. Colour yellow to pale brown. Rectangular shape characteristic. Widespread.

Key characteristics

  • A tumid, roughly rectangular shell
  • Umbos broad and swollen and lying behind the mid point
  • Surface glossy with fairly strong, irregular, concentric striae
  • Colour yellow to pale brown



World Distribution

Distribution type: Circumpolar Wide-temperate (66).

GBIF distribution map [open in new tab]

Irish Distribution

Widespread but becoming slightly rarer towards the north coast and commonest on the central plain.


  • Widespread in slow-moving water of rivers, streams and drains
  • Found in some lake margins
  • Although not excluded from more acid waters, generally rare in the highlands

Red List status

  • Least concern (lc).

Wikipedia link

Wikipedia page for Pisidium milium

 Anderson, R., (2016). Pisidium milium Held 1836. [In] MolluscIreland. Accessed on 2024-03-02.