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Montana Field Guide

Montana Field Guides

Silky Vallonia - Vallonia cyclophorella


Global Rank: G5
State Rank: SNR

Agency Status
USFWS:
USFS:
BLM:


 

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General Description
A small shell, to 3.4 mm diameter and 1.4 mm in height, flattened heliciform with regularly spaced blade-like axial ribs, about 3 1/2 whorls, the last descending at the aperture. Shell coloration is translucent whitish, gray or pale brown. Aperture lip is abruptly flared but not thickened with an internal callus; umbilicus wide, about 1/2 to 1/3 the shell diameter. Animal is white (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. An unthickened lip distinguish V. cyclophorella and V. perspectiva from V. pulchella and V. gracilicosta. V. cyclophorela has regularly spaced blade-like axial ribs, and an umbilicus about 1/3 the shell diameter while V. perspectiva has evenly-spaced ribs and an umbilicus about 1/2 the shell diameter. V. cyclophorella is similar in structure to Vallonia perspectiva but larger (up to 3.4 mm diameter compared to 2.0 mm, respectively).

Species Range
Montana Range

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Range Comments
Western North America from Alaska to the southwestern United States, east to Alberta, North Dakota and Texas (Forsyth 2004, Burke 2013). In Montana, reported on both sides of the Continental Divide from 12 counties: Beaverhead, Gallatin, Granite, Lake, Lewis and Clark, Lincoln, Meagher, Missoula, Park, Powell, Stillwater, Teton. Elevation range is 1320 to 2300 m (4330 to 7545 ft). May be locally common; 23 were found at one Teton County site in early August (Hendricks 2012).

Summary of Observations Submitted for Montana
Number of Observations: 26

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Relative Density

Recency

 

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


Predicted Distribution in Montana
Predicted distribution model for Silky Vallonia (Vallonia cyclophorella). Records were spatially unique and had a locational uncertainty of ≤ 400 meters.  Hotter colors indicate areas that are predicted to have more suitable habitat for the species.  Black dots are positive data used to build the model.  Gray dots are locations where a survey capable of detecting the species has been performed.  Landownership, a shaded relief map, and county lines are included for reference.  Details of the modeling effort, a description of the environmental layers used, and a more thorough interpretation of model outputs can be found in the report Land Mollusk Surveys and Predicted Distribution Models on USFS Northern Region Lands: 2007.

Predicted Distribution Map

More model output for this species
Habitat
Drier mixed conifer forest and open grassy and rocky slopes. Canopy species include Douglasfir, Engelmann spruce, western larch, lodgepole pine, black cottonwood, aspen, and Rocky Mountain juniper. Found under woody debris, rocks, and in leaf litter (Forsyth 2004, Hendricks 2012, Burke 2013).

References
  • 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.
    • Frest, T.J. and E.J. Johannes. 2001. An annotated checklist of Idaho land and freshwater mollusks. Journal of the Idaho Academy of Science 36(2):1-51.
    • Henderson, J. 1933. Mollusca of the Yellowstone Park, Teton Park and Jackson Hole region. Nautilus 47:1-3.
    • 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.
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Citation for data on this website:
Silky Vallonia — Vallonia cyclophorella.  Montana Field Guide.  .  Retrieved on , from