Patera appressa

Patera (Patera) appressa (Say, 1821)
Flat Bladetooth

  • Helix appressa Say 1821: 151.
  • Helix linguifera A. Férussac 1821 (1821–1822): 33, nomen nudum.
  • Helix linguifera A. Férussac 1823 in A. Férussac & Deshayes 1819–1851: pl. 49a, fig. 3.
  • Polygyra appressa sculptior Chadwick 1899: 54.
  • Helix santageorgiensis Pilsbry 1940: 752, fig. 452c.
  • Polygyra appressa var. extrema MacMillan 1940: 98.
Patera appressa
Patera appressa; Trenton, Ontario.

Identification. Shell subdiscoid, pale brown, weakly glossy, opaque. Spire low, domed; apex bluntly rounded. Whorls ca 4½, regularly increasing in width. Suture moderately impressed. Periphery rounded, slightly shouldered, medial on last whorl. Protoconch with microscopic irregular spiral striae evident in places. Teleoconch with narrow, close-spaced, somewhat irregular colabral threads, incremental striae; weak spiral striae evident in places. Last whorl descending close to the peristome; constriction of whorl behind the baso-palatal lip; crest negligible. Umbilicus entirely sealed by a conspicuous, white callus, an expansion of the columellar lip. Aperture subovate. Apertural dentition: 1 long slightly curved parietal denticle. Palatal and basocolumellar lip abruptly expanded, thickened, not recurved; basocolumellar lip with ridge-like callus, truncate before reaching palatal lip. Parietal callus glazed, transparent, inconspicuous. Aperture lip and parietal denticle white. Shell width 15.0–18.3 mm.

Habitat. In highly disturbed urban wooded hill and in a naturalized urban park.

Global range. Southern Appalachians: specifically southern Ohio, West Virginia, Virginia, eastern Kentucky, eastern Tennessee, North Carolina, and north-eastern South Carolina; additional records from other states as far west as Indiana and Oklahoma and north to Maryland (Hubricht 1985, Martin & Bergey 2013); Bermuda (Bieler & Slapcinsky 2000, Forsyth et al. 2015); Ontario.

Canadian range. Introduced to Trenton, Hastings County, Ontario: several places along the Moira River and at The Mountain (Forsyth et al. 2015).

Forsyth et al. (2015) explained the history of the discovery of this species at Trenton, Ontario, and its previous identification and first report from Canada by Grimm (1996) as Patera cf. panselena (Hubricht, 1976). They concluded that the Canadian population is a probable introduction.

Etymology. Latin, appressus, “pressed in”, possibly in reference to the umbilical area.

Remarks. Within this species, Pilsbry (1940, as Mesodon appressus) included several “forms”: M. appressus linguiferus, sculptior, sanctageorgiensis, laevior and extremus. None of these taxa are in use today as either species or subspecies, except for laevior, which Hubricht (1968, 1985) considered to be a distinct species, Patera laevior (Pilsbry, 1940).