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Montana Field Guide

Montana Field Guides

Multirib Vallonia - Vallonia gracilicosta
Other Names:  Vallonia costata montana, Vallonia albula, Vallonia sonorana

Native Species

Global Rank: G5
State Rank: S4S5

Agency Status


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General Description
A small shell, to about 2.9 mm diameter and 1.2 mm in height, flatten heliciform with widely-spaced lamellar axial ribs, about 3 to 3 1/2 whorls, the last strongly expanding and descending to the aperture. Shell coloration is translucent whitish to pale brown. Aperture lip thickened inside with a broad opaque-white rib; umbilicus wide, about 1/3 to 1/2 the shell diameter. Animal is white. Reports of Vallonia costata by Berry are attributed by Henderson to this species (Hendricks 2012, Burke 2013).

Diagnostic Characteristics
Combination of small size (< 3.5 mm diameter), flattened heliciform shape, flared lip, and color (translucent white to pale brown) separate Vallonia from other shells. A thickend lip distinguish V. pulchella and V. gracilicosta from V. cyclophorella and V. perspectiva. V. pulchella has occasional low wrinkles but is unribbed and shiny while V. gracilicosta has widely-spaced axial ribs.

Species Range
Montana Range Range Descriptions


Range Comments
North America south through the northern Midwest and Rocky Mountain states to Arizona and New Mexico (Forsyth 2004, Burke 2013). In Montana, reported on both sides of the Continental Divide (but mostly east) from 12 counties: Broadwater, Carbon, Carter, Fergus, Gallatin, Golden Valley, Lincoln, Madison, Powder River, Stillwater, Wheatland, Wibaux. Elevation range is 823 to 2149 m (2700 to 7050 ft). May be abundant in some sites; 64 shells (live and dead) were reported at one Fergus County site in early October (Hendricks 2012).

Observations in Montana Natural Heritage Program Database
Number of Observations: 46

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density



(Observations spanning multiple months or years are excluded from time charts)

Moist and drier forested sites, aspen stands. Canopy species include aspen, green ash, Douglasfir, ponderosa pine, western larch, Engelmann spruce, western redcedar, subalpine fir, limber pine; secondary canopy includes dogwood, and hawthorn. Found under woody debris and rocks, in leaf litter and duff (Hendricks 2012).

  • Literature Cited AboveLegend:   View Online Publication
    • Burke, T. E. 2013. Land snails and slugs of the Pacific Northwest. Corvallis, OR: Oregon State University Press. 344 p.
    • Forsyth, R.G. 2004. Land snails of British Columbia. Royal British Columbia Museum: Victoria, British Columbia, Canada. 188 pp.
    • Hendricks, P. 2012. A Guide to the Land Snails and Slugs of Montana. A report to the U.S. Forest Service - Region 1. Montana Natural Heritage Program, Helena, MT. vii + 187 pp. plus appendices.
  • Additional ReferencesLegend:   View Online Publication
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    • Beetle, D. E. 1961. Mollusca of the Big Horn Mountains. The Nautilus 74:95-102.
    • Beetle, D.E. 1997. Recolonization of burned aspen groves by land snails. Yellowstone Science 5 (summer):6-8.
    • Berry, S.S. 1913. A list of Mollusca from the Mussellshell Valley, Montana. Nautilus 26:130-131.
    • Berry, S.S. 1916. Notes of Mollusca of central Montana. Nautilus 29:124-128.
    • Henderson, J. 1936. Mollusca of Colorado, Utah, Montana, Idaho, and Wyoming, supplement. University of Colorado Studies 23(2): 81-145.
    • Pilsbry, H.A. 1948. Land Mollusca of North America (north of Mexico), Volume II Part 2. The Academy of Natural Sciences of Philadelphia Monograph Number 2(2): 521-1113.
    • Squyer, H. 1894. List of shells from the vicinity of Mingusville, Montana. The Nautilus 8:63-65.
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Citation for data on this website:
Multirib Vallonia — Vallonia gracilicosta.  Montana Field Guide.  .  Retrieved on , from