Description: Shell small, chalky-white, very flattened-depressed with conspicuous radial ribs. Like other Vallonia the umbilicus is very wide. Aperture is almost circular but inclined downwards. The lip is thickened and reflected. Whorls are slightly angular at the periphery with deep sutures. Widespread but local. 2.3-2.5 mm.

World Distribution: Very widely distributed in Europe and across Eurasia to North America. Distribution type: Circumpolar Wide-temperate (66).

Irish Distribution: Common on the Carboniferous limestone of the southern part of the central plain but more local northwards and entirely coastal outside limestone areas, particularly in the north.

Ecology:

• The grass snails are restricted to open situations
• Moderately thermophilic preferring light vegetation and the presence of basic rocks
• In northern counties restricted to calcareous sands or rocks along the coast

Key Identification Features:

• A very small, flattened, ivory-white shell
• Ornamented with conspicuous and regularly spaced ribs
• Umbilicus very wide
• Apertural lip thickened and reflected
• Shell solid, not fragile
• Whorls slightly angular at the periphery with deep sutures

Red list status:

• Least concern (lc).

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

iNaturalist: Vallonia costata at iNaturalist World Species Observations database.

GBIF data for Vallonia costata | Classification: Gastropoda, Stylommatophora, Valloniidae, Vallonia

Thumbnails for genus Vallonia