MolluscIreland - land and freshwater
  • Pisidium amnicum (O. F. Müller 1774) River pea shell
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Pisidium amnicum
© Dr Roy Anderson

Map hosted by the National Biodiversity Data Centre, Waterford
To view the species profile on Biodiversity Maps and access the live map, please click on the map.


The largest Pisidium species. Shell a triangular oval with low umbos in front of the middle. Surface with glossy periostracum and prominent, irregularly spaced concentric ribs. Colour greyish white to brown often with a greenish cast, particularly towards the ventral margin. Widespread in hard water river systems.

Key characteristics

  • Large for a Pisidium at 11 mm.
  • Shell fairly solid, a triangular oval shape
  • Umbos broad but not prominent
  • Shell ornamented by an irregular concentric sculpture
  • Colour greyish white to brown often with a greenish cast, glossy
  • Umbos often coated with a dull ferruginous deposit


7-11 mm.

World Distribution

Found across the Palaearctic and Nearctic. Distribution type: Circumpolar Boreo-temperate (56).

GBIF distribution map [open in new tab]

Irish Distribution

Locally common in the centre and south-east and, more rarely, as far north as the Lough Erne and Lough Neagh catchments.


  • Prefers relatively hard flowing water
  • Usually found on gravelly or sandy bottoms with a moderate flow
  • Relatively intolerant of pollution

Red List status

  • Least concern (lc).

Wikipedia link

Wikipedia page for Pisidium amnicum

 Anderson, R., (2016). Pisidium amnicum (O. F. Müller 1774). [In] MolluscIreland. Accessed on 2024-03-02.