Keys to Polygyridae of Canada

For simplicity, and following Pilsbry’s lead (1939, 1940), the eastern and western genera and species are keyed separately.

This key will serve to identify mature individuals only. Variation in the presence of a parietal tooth or periostracal hairs require some species to be keyed out more than once.

1a Poorly to strongly developed parietal denticle present in adults (it may be only a small, opaque whitish callus) — 2
Parietal denticle altogether absent — 5

2a Parietal denticle generally rather well-developed. Periostracum hirsute in some — 3
2b Parietal denticle weak, just a slight callus. Periostracum never hirsute. (Presence of a parietal denticle is very occasional in this species.) — Allogona ptychophora, in part

3a Mature w < 9 mm. Palatal lip rather thin, strongly flared but not recurved. Parietal denticle, in basal view, long and curved. Periostracal hairs generally persistent in adults — Cryptomastix germana
3b Mature shell width ≥ 12 mm. Palatal lip thicker, expanded, and recurved. Parietal denticle short-elongate to tubercular. Periostracal hairs usually not persistent in adults; if they are present, then short and relatively sparsely spaced — 4

4a Mature shell width ≤ 26 mm, slightly depressed-globose. Historically southwest, coastal British Columbia — Cryptomastix devia
4b Mature w ≤ 19 mm, usually rather more depressed-globose. South and southeast interior of British Columbia — Cryptomastix mullani, in part

5a Periostracum hirsute — 6
Periostracum not hirsute — 7

6a A few weak spiral striae present. Palatal lip recurved. Periostracal hairs densely spaced, rather long — Cryptomastix mullani, in part
6b Spiral striae absent. Palatal lip flared outward but not strongly recurved. Periostracal hairs densely spaced, rather long — Vespericola columbianus 

7a Mature shell width < 19 mm. Periostracum hirsute in some. (Absence of the parietal denticle is occasional in this species, even in otherwise adult shells.) — Cryptomastix mullani, in part
7b Mature shell width 19–35 mm. Periostracum never hirsute — 8

8a Mature shell width 19–24 mm. Malleated sculpture less pronounced; colabral riblets more even and better formed. A weak parietal denticle occasionally present. Southern Interior of British Columbia — Allogona ptychophora
Mature shell width 23–35 mm. Malleated sculpture generally stronger; colabral riblets less well-formed. Never with a parietal denticle. Lower Fraser Valley and southern Vancouver Island — Allogona townsendiana

This key will serve to identify mature individuals only.

This key will serve to identify mature individuals only. This key has not been so extensively tested as the preceding key and caution should be exercised when using it.

1a Umbilicus absent, completely covered by a callus or an extension of the baso-columellar lip — 2
1b Umbilicus present: may be broad, small, or very narrow and partially occluded by the baso-columellar lip — 11

2a Parietal denticle present — 3
2b Parietal denticle absent — 7

3a Aperture clearly with 3 denticles: a parietal, a basal (which may be long and ridge-like), and a clearly developed palatal — 4
♦ Caution: If there is a ‘thickening’ of the lip in place of a well-defined palatal denticle, use couplet “b”.
3b Aperture not as in “a”; with one denticle (parietal) or two denticles (parietal and basal) — 5

4a Basal denticle long, ridge-like. Mature width > 19 mm — Xolotrema denotatum
4b Basal denticle rather tubercular. Mature width ≤ 8–12 mm — Inflectarius inflectus

5a Aperture narrow and ± directed basally (or “downward”). Basal lip with a small notch — Stenotrema barbatum
5b Aperture usually broader (but still may be somewhat narrowed) and usually not so strongly directed basally (“downward”). Basal lip without a notch — 6

6a Parietal denticle long and curved, joined to the umbilical callus — Patera appressa
Parietal denticle shorter, not joined to the umbilical callus — Neohelix dentifera

7b Baso-columellar lip more-or-less straightened (or slightly concave), often with a low protuberance — 8
Baso-columellar lip curved — 9

8a Maximum width < 20 mm — Patera pennsylvanica
8b Maximum width ≥ 20 mm — Neohelix albolabris

9a Maximum width > 20 mm. With narrow reddish brown spiral bands/lines — Webbhelix multilineata
Maximum width < 17 mm. Not banded — Mesodon spp., in part

11a No parietal denticle — 12
Parietal denticle present — 13

12a Basal lip with a low denticle-like callus — Allogona profunda
12b Without a denticle-like callus — Mesodon spp., in part

13a Aperture with three denticles: a parietal, a basal, and a clearly developed palatal  — 14
♦ Caution: If there is a weak “thickening” of the lip in place of a well-defined palatal denticle, use couplet “b”)
Aperture not as in “a”; with one denticle (parietal) or two denticles (parietal and basal) — 15

14a Palatal denticle flush with the palatal lip — Triodopsis tridentata
14b Palatal denticle receding or bent inward — Triodopsis vulgata

15a Aperture rather narrow (in apertural view), narrowed significantly by the parietal denticle  16
15b Aperture broader — 17

16a Shell generally smaller: width ≈ 5.5–9 mm. Umbilicus rather broadly open. Spire whorls more tightly coiled — Euchemotrema leaii
Shell generally larger: width ≈ 10 mm. Umbilicus rather narrow, nearly closed by the columellar lip. Spire whorls not so tightly coiled — Euchemotrema fraternum

17a Umbilicus open. Basal lip with a small, rather sharply tubercular denticle and surface sculpture of sharp, close-spaced threads — Appalachina sayana
17b Umbilicus partly covered but not fully closed by the basal lip. Basal denticle absent, blade-like or swollen. Surface nearly smooth or lightly striate — Mesodon spp., in part