Polygyridae

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.


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)


Key to Western Canadian (British Columbia) Polygyridae

1a       Parietal denticle present (sometimes just a low callus) — 2

1b       Parietal denticle (or callus) absent —  5

2a       Parietal denticle a low, white callus (a rare condition) — Allogona ptychophora

2b       Parietal denticle well developed, high, and often long — 3

3a       Shell width to ca 8 mm. Periostracal hairs persistent in adults. Parietal callus long, somewhat filling most of aperture. Flared adult lip rather thin-edged — Micranepsia germana

3b       Shell larger, width >17 mm. Periostracal hairs not normally persisting in adults. Parietal callus rather short. Flared or recurved adult lip rather thickened —  4

4a       Shell flattened; spire low. Southern interior of BC — Cryptomastix mullani

4b       Shell subglobose; spire conical. Historically, southern coastal BC — Cryptomastix devia

5a       Periostracum never hairy. Shell with coarse colabral threads, wrinkles, or ribs, sometimes malleated. Minute spiral striae (when not eroded away)6

5b       Periostracum usually hairy, sometimes not. Shell with fine colabral wrinkles, no spiral striae — Vespericola columbianus

6a       Shell width to 24 mm. Malleated sculpture usually absent —  Allogona ptychophora

6b       Shell width to 35 mm. Malleated sculpture often strong — Allogona townsendiana


Subfamily Triodopsinae Pilsbry, 1940

Tribe Triodopsini Pilsbry, 1940

Genus Triodopsis Rafinesque, 1819

  • Triodopsis Rafinesque 1819: 425; type species by original designation: Helix tridentata Say, 1817

Etymology. Greek: trios, three + odon, tooth + opsis, appearance; feminine.


Subgenus Triodopsis Rafinesque, 1819

Triodopsis (Triodopsis) tridentata (Say, 1817)


Subgenus Shelfordorbis Webb, 1959

  • Shelfordorbis Webb 1959: 24. Type species by original designation: Triodopsis fraudulenta vulgata Pilsbry, 1940.

Described as a section of Triodopsis by Webb (1959), Emberton (1995) elevated it to the status of subgenus.

Etymology. Named for Victor Shelford, University of Illinois, under whom Glenn R. Webb studied + Latin: orbis, disc or coil (Emberton 1995).

Triodopsis (Shelfordorbis) vulgata Pilsbry, 1940


Genus Webbhelix Emberton, 1988

  • Webbhelix Emberton 1988: 163, 188. Type species by monotypy: Helix multilineata Say, 1821.

One or two species in central North America; one species occurs north into just barely into southern Ontario.

Etymology. Named after Glenn Robert Webb (1918–1999), American malacologist and publisher of the privately published malacological journal Gastropodia (Kabat & Petit 2007), + Greek helix, “a spiral”. The gender is feminine.

Webbhelix multilineata (Say, 1821)


Genus Xolotrema Rafinesque, 1819

  • Xolotrema Rafinesque 1819: 425; type species by subsequent designation (Pilsbry 1940: 823): Helix notata Deshayes, 1830 (= Xolotrema denotatum, but see footnote; Pilsbry 1940).

There are five species, belonging to two subgenera (including the nominotypical subgenus), in the eastern United States, with one of these species extending north into southwestern Ontario. Pilsbry had treated Xolotrema as a subgenus of Triodopsis, but Emberton (1988) raised it to a full genus and recognized two subgenera.

Etymology. Greek xolos, “hollow” + trema, “aperture” or “hole”; neuter.


Subgenus Xolotrema Rafinesque, 1819

Xolotrema (Xolotrema) denotatum (A. Férussac in A. Férussac & Deshayes, 1823)


Tribe Allogonini Emberton, 1995

Genus Allogona Pilsbry, 1939

  • Allogona Pilsbry 1939: xvii; type species by original designation: Helix profunda Say, 1821.

Etymology. Greek allos, “other” or “different” + gona, “genitalia”; feminine.


Subgenus Allogona Pilsbry, 1939

Allogona (Allogona) profunda (Say, 1821)


Subgenus Dysmedoma Pilsbry, 1939

  • Dysmedoma Pilsbry 1939: xvii; type species by original designation: Allogona townsendiana (I. Lea, 1839).

Etymology. Greek, Dysme, sunset + doma, house—a reference to the western distribution of the subgenus (Pilsbry 1939).

Allogona (Dysmedoma) ptychophora (A. D. Brown, 1870)
Allogona (Dysmedoma) townsendiana (I. Lea, 1838)


Genus Cryptomastix Pilsbry, 1939

  • Cryptomastix Pilsbry 1939: xvii; type species by original designation: Polygyra mullani olneyae.

Pilsbry (1940) proposed Cryptomastix as a subgenus of Triodopsis, but later, Emberton (1995) differentiated the western species from the eastern, true Triodopsis and elevated the western Cryptomastix to genus.

Etymology. Greek, kryptos, hidden + mastix, flagellum.


Subgenus Cryptomastix Pilsbry, 1939

Cryptomastix (Cryptomastix) devia (Gould, 1846)
Cryptomastix (Cryptomastix) mullani (Bland & Cooper, 1861)


Tribe Mesodontini Tryon, 1866

Genus Inflectarius Pilsbry, 1940

  • Inflectarius Pilsbry 1940: 776; type species by original designation: Mesodon inflectus (Say, 1821).

Etymology. Derived from inflectus,the name of the type species.


Subgenus Inflectarius Pilsbry, 1940

Inflectarius (Inflectarius) inflectus (Say, 1821)


Genus Mesodon A. Férussac, 1821

  • Mesodon A. Férussac 1821 (1821–1822): 37 (folio edition), 33 (quarto edition); type species by monotypy (ICZN 1992, Opinion 1691): Helix thyroidus Say, 1817.

Etymology. Greek mesos, “middle”, + odon, “tooth”. The gender is masculine.

Subgenus Appalachina Pilsbry, 1940

  • Appalachina Pilsbry 1940: 762; type species by original designation: Polygyra sayana Pilsbry in Pilsbry & Ferriss, 1906.

Etymology. Named for Appalachia, the mountainous region in eastern North America; feminine.

Mesodon (Appalachina) sayanus (Pilsbry in Pilsbry & Ferriss, 1906)


Subgenus Mesodon A. Férussac, 1821

Mesodon (Mesodon) thyroidus (Say, 1817)


Subgenus Aphalogona Webb, 1954

  • Aphalogona Webb 1954: 19; type species by original designation: Mesodon elevatus (Say, 1821).

Etymology. Webb intended name to mean “penis without a chalice”, but Emberton (1991) derived it differently: Greek a- without + phalos shining; error for lophos, crest + gona,error for gone, that which produces seed, incorrectly translated as sex organ.

Mesodon (Aphalogona) zaletus (A. Binney, 1837)


Genus Neohelix Ihering, 1892

  • Neohelix Ihering 1892: 482; type species by subsequent designation (Pilsbry 1930: 326): Helix albolabris Say, 1817.

Pilsbry (1940) treated Neohelix as a subgenus of Triodopsis. Emberton (1988) subsequently regarded Neohelix as a separate genus and later (Emberton 1995) established subgenera.

Etymology. Greek: neo, new or recent + helix, a spiral.


Subgenus Neohelix Ihering, 1892

Neohelix (Neohelix) albolabris albolabris (Say, 1817)


Subgenus Asamiorbis Emberton, 1995

  • Asamiorbis Emberton 1995: 78; type species by original designation: Helix dentifera A. Binney, 1837.

Emberton (1995) established this subgenus for Neohelilx dentifera and related species.

Etymology. Named after the Japanese land snail ecologist and geneticist, Dr Takahiro Asami + Latin: orbis,disc or coil.

Neohelix (Asamiorbis) dentifera (A. Binney, 1837)


Genus Patera Albers, 1850

  • Patera Albers 1850: 96; type species by subsequent designation (Pilsbry 1930: 326): 96.

Etymology. Latin: a saucer; feminine.


Subgenus Patera Albers, 1850

Patera (Patera) appressa (Say, 1821)


Subgenus Ragsdaleorbis Webb, 1954

  • Ragsdaleorbis Webb 1954: 20; type species by original designation: Mesodon pennsylvanicus (Green, 1827).

Webb (1954) established this taxon as a subgenus of Mesodon, but Emberton (1991) later transferred it to Patera, giving it subgenus rank.

Etymology. Named after John P. Ragsdale, Jr (Indianapolis, Indiana), a boyhood friend of malacologist Glenn Webb (Emberton 1991) + Latin: orbis, a disc or a coil.

Patera (Ragsdaleorbis) pennsylvanica (Green, 1827)


Tribe Stenotrematini Emberton, 1995

Genus Euchemotrema Archer, 1939

  • Euchemotrema Archer 1939: 98; type species: Stenotrema monodon (Rackett, 1821) = E. leaii (A. Binney, 1840).

Pilsbry (1940) treated Euchemotrema as a “section” of Stenotrema. Later, Emberton (1995) raised Euchemotrema to genus rank, separate from Stenotrema.

Etymology. Greek, eu, good + cheno, gaping + trema, aperture or hole; neuter.

Euchemotrema fraternum (Say, 1824)
Euchemotrema leaii (A. Binney, 1840)


Genus Stenotrema Rafinesque, 1819

  • Stenotrema Rafinesque 1819: 425; type species by monotypy: Stenotrema convexa Rafinesque, 1819 (nomen nudum) = Stenotrema stenotrema L. Pfeiffer, 1842 (Pilsbry 1930). Stenostoma Rafinesque 1831: 3; type species by monotypy: Stenotrema convexa Rafinesque, 1819.

Etymology. Greek: stenos, narrow + trema, aperture or hole. Neuter.


Subgenus Toxotrema Rafinesque, 1819

  • Toxotrema Rafinesque 1819: 425; type species by subsequent designation (Pilsbry 1930): Toxotrema globularis Rafinesque, 1819 (nomen nudum) = Helix hirsuta Say, 1817 (Pilsbry 1930).
  • Toxostoma Rafinesque 1831: 3; type species by subsequent designation (Pilsbry 1930): H. hirsuta Say, 1817.

Etymology. Greek: toxo, a bow, + trema, aperture or hole. Neuter.

Stenotrema (Toxotrema) barbatum (G. H. Clapp, 1904)


Tribe Vespericolini Emberton, 1995

Genus Micranepsia Pilsbry, 1940

  • Micranepsia Pilsbry 1940: 872; type species by original designation: Triodopsis germana.

Etymology. Greek: mikros, little + anepsia, cousin. Pilsbry (1940) thought this to be “a little cousin” of Cryptomastix. The gender is feminine.

Micranepsia germana (Gould in A. Binney, 1851)

Genus Vespericola Pilsbry, 1939

  • Vespericola Pilsbry 1939: xvii; type species by original designation: Polygyra columbiana pilosa Henderson, 1928 [= V. pilosus (Henderson, 1928); Roth & Miller 1993].

Etymology. Latin: vesper,evening or west + colo, to inhabit; thus, “dwellers in the evening or west” (Pilsbry 1940: 892). Roth & Miller (1993) treated the name as masculine.

Vespericola columbianus (I. Lea, 1839)