Family Polygyridae Pilsbry, 1895
The Polygyridae are a large group of New World snails which occur in temperate, subtropical, and tropical parts of North America south to northern Central America, on some islands in the Caribbean, and in Bermuda. It is a large and diverse family showing wide variety of adaption and convergence of shell morphology (see especially Emberton 1988, 1991, 1994, 1995). The feature in common with all polygyrids is the presence of an outwardly, often strongly, flared outer lip. Apertural denticles are present certain groups, although sometimes variably. At least 21 species of polygyrids are native to Canada, although one or possibly two of these are now extirpated. There is an additional species, Patera appressa, which is believed to have been introduced.
Species in Canada Allogona (Allogona) profunda (Say, 1821) Allogona (Dysmedoma) ptychophora (A. D. Brown, 1870) Allogona (Dysmedoma) townsendiana (I. Lea, 1839) Cryptomastix (Cryptomastix) devia (Gould, 1846) Cryptomastix (Cryptomastix) mullani (Bland & Cooper, 1861) Euchemotrema fraternum (Say, 1824) Euchemotrema leaii (A. Binney, 1840) Inflectarius (Inflectarius) inflectus (Say, 1821) Mesodon (Aphalogona) zaletus (A. Binney, 1837) Mesodon (Appalachina) sayana (Pilsbry in Pilsbry & Ferriss, 1906) Mesodon (Mesodon) thyroidus (Say, 1817) Micranepsia germana (Gould in A. Binney, 1851) Neohelix (Asamiorbis) dentifera (A. Binney, 1837) Neohelix (Neohelix) albolabris (Say, 1817) Patera (Patera) appressa (Say, 1821) ◆ Patera (Ragsdaleorbis) pennsylvanica (Green, 1827) Stenotrema (Toxotrema) barbatum (G. H. Clapp, 1904) Triodopsis (Shelfordorbis) vulgata Pilsbry, 1940 Triodopsis (Triodopsis) tridentata (Say, 1817) Vespericola columbianus (I. Lea, 1839) Webbhelix multilineata (Say, 1821) Xolotrema (Xolotrema) denotatum (A. Férussac in A. Férussac & Deshayes, 1823) ◆ = introduced