Vitrina pellucida (O. F. Müller, 1774)
- Helix pellucida O. F. Müller 1774: 15, 215; partim.
- Vitrina exilis Morelet 1858: 8.
- Vitrina pfeifferi Newcomb 1861: 92.
- Vitrina alaskana Dall 1905: 92, nomen novum pro Vitrina pfeifferi Newcomb, 1861.
- ? Vitrina pellucida islandica Forcart 1955: 160, figs 2, 3, pl. 12, figs 3, 6.
Identification. Shell depressed subglobose, very thin, delicate. Whorls 2½–3, rapidly enlarging. Spire low, domed. Protoconch smoothish, with microscopic punctae in spiral rows. Teleoconch with irregular, microscopic striae which are more wrinkle-like near suture. Aperture capacious, subovate, edentulous. Lip thin, simple. Shell translucent yellow-green to nearly transparent and colourless (more opaque and whitish when weathered).
This species is anatomically distinguished from V. angelicae in having the penis mostly enclosed by a sheath and in having the base of the duct of the bursa copulatrix swollen.
Shells of the two species are probably indistinguishable, although according to Pilsbry (1946) V. pellucida is a little less flattened than V. angelicae (he used different names for both) and with the microscopic punctae on the protoconch in regular, spiral rows.
Animal variable in colour: pale grey or brownish and quite dark, with darker head and tentacles.
Habitat. In open places, such as gravelly and grassy roadsides, meadows and prairies, alpine and arctic tundra, and in open woods; under rocks and dead wood but often crawling in the open during cool, wet weather.
Global range. Western North America, across northern Asia and Europe, and Iceland.
Canadian range. British Columbia east at least to southern Manitoba; north into Yukon and Northwest Territories.
Etymology. Latin, pellucidus, “transparent”.
Remarks. This species in western North American has long been called V. alaskana, but some authors realised that it was anatomically indistinguishable from V. pellucida and treated alaskana as a subspecies (e.g. Bequaert & Miller 1973, Sysoev & Schileyko 2009) or synonym (Roth & Lindberg 1981, Roth & Sadeghian 2003).
Forcart (1955) recognized two subspecies, V. pellucida pellucida and V. pellucida islandica Forcart 1955 based on the relative proportions of the genital organs. He distinguished islandica by its longer penis with the sheath extending further distally, the longer and slimmer vas deferens, the more strongly, spherically swollen base of the bursa copulatrix duct, and the shorter atrium. If these characters or others are found to support separation of the species into subspecies, the North American populations could belong to the nominal subspecies, V. pellucida pellucida.