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Thin-lip Vallonia - Vallonia perspectiva
General Description
A very small and thin shell, to about 2 mm diameter and 0.8 mm in height, flattened heliciform, with a series of evenly spaced ribs, to about 3 1/3 whorls, gradually increasing in size and flattened above and below the periphery, the last rapidly descending, suture deep. Shell coloration is translucent pale amber to colorless. Aperture is inclined, oblique-ovoid, without a thickened lip; umbilicus wide, about 1/2 the shell diameter. Animal is white (Hendricks 2012).
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
Range Descriptions
Native
Range Comments
North America throughout the eastern and southwestern United States to Mexico. In Montana, reported east of the Continental Divide only from Wibaux County, elevation 823 m (2700 ft)(Squyer 1894, Hendricks 2012). Range and abundance in Montana poorly understood; current status needs investigation. Identification questionable. The Wibaux County record (Squyer 1894) was attributed by Henderson (1924) to Vallonia parvula, whereas Pilsbry (1948) made no mention of the Wibaux County record in his accounts of V. perspectiva or V. parvula.
Observations in Montana Natural Heritage Program Database
Number of Observations: 1
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Relative Density
Recency
(Observations spanning multiple months or years are excluded from time charts)
Habitat
Driers sites on hillsides, rocky outcrops, near springs, and streamside riparian habitat, including cottonwood and willow. Found under rocks and woody debris, in leaf litter, and drift material (Hendricks 2012). Habitat in Montana poorly documented.
Stewardship Responsibility
References
- Literature Cited AboveLegend:
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Henderson, J. 1924. Mollusca of Colorado, Utah, Montana, Idaho, and Wyoming. University of Colorado Studies 13(2):65-223.- 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.
- 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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