Allogona townsendiana

The adult shell is large (width, 28-35 mm), globose, and pale brown or straw-yellow. There are 5¼-6 whorls that bear irregular, light- coloured, wrinkle-like axial riblets and exceedingly fine, wavy spiral striae. Irregular dimpled sculpture is usually present. The fine spiral striae are often not evident on eroded shells that lack the outer, periostracal layer. The periostracum does not have fine hair-like structures present in some polygyrid snails. The apertural lip is white, thickened, and strongly flared outward. Basally the lip is heavier with a slight bulging callus at its junction with the columellar lip, but there is no denticle within the aperture (COSEWIC, 2002).

The Pacific Sideband (Monadenia fidelis), for example, is a large, brightly coloured, banded species quite unlike A. townsendiana. The most likely confusion is with other polygyrid snails, all of which have the distinctly flared or recurved apertural lip. The Idaho Forestsnail (A. ptychophora) is very similar but the shell is slightly smaller, rarely malleated, and has more clearly developed axial riblets. In Canada, the ranges of the two species are allopatric; A. ptychophora occurs in southeastern British Columbia and southern Alberta. The Puget Oregonian (Cryptomastix devia) and Pygmy Oregonian (C. germana) are recognized by the presence of a denticle within the aperture of adult shells. Both the Northwest Hesperian (Vespericola columbianus) and C. germana are much smaller (<16 mm and <7 mm, respectively) and have a hairy periostracum (COSEWIC, 2002).

Habitat requirements of A. townsendiana are poorly known. It occupies mixedwood and deciduous forests, typically dominated by Bigleaf Maple (Acer macrophyllum). Allogona townsendiana probably requires coarse woody debris, copious amounts of leaf litter, and both living and senescent vegetation. Shade provided by the forest canopy conserves moisture and ameliorates fluctuations in temperature and moisture conditions on the forest floor. Aestivating and hibernating snails require shelter, but the exact habitat attributes required for these functions are unknown (COSEWIC, 2002). The life cycle is characterized by slow maturation and mating has been tied to close proximity to coarse woody debris and presence of the stinging nettle, Urtica dioica (Steensma et al., 2009).

Allogona townsendiana is a simultaneous hermaphrodite and lays eggs. Oviposition occurs in spring but may not be restricted to this season. The snails are most active during spring (Kozloff 1976), which is apparently correlated with mating and oviposition. These snails dig a depression into soft, moist soil and lay multiple eggs (Ovaska et al. 2001a). Clutch size is unknown, and nothing further is known about breeding requirements. Characteristics of the soil and litter layer may be important for oviposition sites (COSEWIC, 2002). In Fort Langley, British Columbia, mating peaked in March and April with adults aggregated in clusters of 8 to 14 before mating, nesting peaked in April-May and resulted in mean clutch size of 34 eggs with hatching 63-64 days after oviposition and juveniles crawling from the nest within hours (Steensma et al., 2009). Snails hibernated from early November to mid-March wihin leaf litter and soil and life span is at least five years (Steensma et al., 2009).