Family Xanthonychidae Strebel & Pfeffer, 1879

There is a single species occurring in Canada, Monadenia fidelis, which is the largest terrestrial snail in the country and a quite remarkably coloured and distinctive species. The genus Monadenia has also been placed in Helminthoglyptidae, Bradybaenidae, and its own family, Monadeniidae.

Species in Canada
Monadenia (Monadenia) fidelis (Gray, 1834)

Subfamily Monadeniinae H. Nordsieck, 1987

Genus Monadenia Pilsbry, 1895

• Monadenia Pilsbry 1895 in 1893–1895: 198; type species by original designation: Helix fidelis Gray, 1834.

Etymology. Greek: monos, one + aden,gland, a reference to the single mucus gland (Pilsbry 1939).

Subgenus Monadenia Pilsbry, 1895