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 structures and limestone. Underneath rocks, debris, boards, dead wood, and vegetation.
Global range. Widespread in Europe north to Scandinavia, south to North Africa, and scattered records east to Lake Baikal, Siberia; north-eastern USA, but west Utah, and parts of south-eastern Canada (Gerber 1996). It is possibly introduced to North America (Forsyth & Nicolai 2019), and Gerber (1996) thought that central and western US records represented recent introductions. It has also been reported from Israel, South Africa, and Australia (Gerber 1996).
Canadian range. Common in southern Manitoba through southern Ontario and southern Quebec. Occurrences in New Brunswick (St Andrews), Alberta (Cypress Hills), and British Columbia (Kamloops) are suspected to be introductions (Forsyth & Nicolai 2019). Quite possibly, the presence of this species in North America represents old introductions.
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”.
- Gerber J (1996) Revision der Gattung Vallonia Risso 1826 (Mollusca: Gastropoda: Valloniidae). Schriften zur Malakozoologie aus dem Haus der Natur – Cismar 8: 1–227.
- 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.