Vallonia costata (O. F. Müller, 1774)
- Helix costata O. F. Müller 1774: 31.
- Many additional synonyms in Europe.
Identification. Shell subdiscoidal, with spire slightly elevated. Whorls few, ca 3. Periphery rounded. Aperture subrotund. Adult lip thickened within by an opaque rib-like callus, expanded and flat-faced. Umbilicus ca 1/3 of shell width. Protoconch usually with indistinct spiral threads (periostracal). Teleoconch with prominent mostly periostracal colabral ribs, ca 28–41 on last whorl; microscopic incremental striae. Shell with a silky sheen, greyish white. Width to ca 2.7 mm (wider than high).
Animal milky white with dark eyespots.
Habitat. Generally, in open, usually rather xeric, anthropogenic habitats: lawns, waste ground, roadsides, meadows, and unkempt gardens. A calciphile; frequently associated with concrete structure and limestone areas. Underneath rocks, debris, boards, dead wood, and vegetation.
Canadian range. Common in southern Manitoba through southern Ontario and southern Quebec. Probably introduced to New Brunswick (St Andrews), Alberta (Cypress Hills), and British Columbia (Kamloops) (Forsyth & Nicolai 2019). It is perhaps possibly introduced to North America (?).
Forsyth & Nicolai (2019) used molecular data to confirm this species from Kamloops, in south-central British Columbia, where it is thought to have been introduced.
Etymology. Latin, costatus, “ribbed”.
- Nicolai A, Forsyth RG (2019) First record of Vallonia costata (O. F. Müller, 1774) (Gastropoda, Eupulmonata, Valloniidae) from British Columbia, Canada, confirmed by partial-COI gene sequence. Check List 15: 287–293.
- Müller OF (1774) Vermium terrestrium et fluviatilium, seu animalium Infusorium, Helminthicorum, et Testaceorum, non marinorum, succincta historia. Volumen alterum: Testacea. Heineck & Faber, Havniæ & Lipsia, xxxvi + 214 + [x] pp.