Description: A small operculate snail with a high, narrow spire when young, but this is lost in adults which become decollate (see images). Surface smooth, matt brownish-white. Animal pale, walking with a looping movement. Confined to gravelly marine foreshores. Galway Bay only. 3.5-5 mm.

World Distribution: On coasts from the British Isles to the Mediterranean and as far east as the Black Sea. Distribution type: Mediterranean-Atlantic (91).

Irish Distribution: Its known distribution encompasses most of the south side of Galway Bay. Added to the Irish List from Carrowmore and Rincarna Lagoons (Nunn et al., 2005) in the inner part of the Bay with five further sites being found at Finavarra, Killeenaran, Parknahallagh and Bishop's Quarter, further to the west. Nicholls (1900) mentions a record of "Truncatella truncatula (Drap.)" for Bundoran in East Donegal where a shell was reportedly taken among shell sand by a Mrs Hancock (fide Thompson (1856)). Jeffreys (1862) regarded the record as a mistake but the finds in Galway Bay may prompt a re-evaluation of this early record.

Ecology:

• Lives on marine foreshores or saltmarshes
• Found sparingly under large stones around high tide level on muddy gravel or stony beaches
• In saltmarshes or by coastal lagoons, occasional under stones among sea purslane or sea blite

Key Identification Features:

• Small operculate shell, narrowly conical when young but decollate (blunt-topped) when adult due to loss of the spire
• Surface brown-white, faintly glossy to dull, smooth (radially channelled or ribbed in some European forms)
• Animal pale, moves by an exaggerated looping movement like a caterpillar

Red list status:

• Critically endangered (CR).

Distribution Map from NBN: Truncatella subcylindrica at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Truncatella subcylindrica at iNaturalist World Species Observations database.

GBIF data for Truncatella subcylindrica | Classification: Gastropoda, Littorinimorpha, Truncatellidae, Truncatella

Thumbnails for genus Truncatella