Gastrocopta (Albinula) holzingeri Sterki, 1889
- Pupa holzingeri Sterki 1889: 37.
- Bifidaria agna Pilsbry & Vanatta 1907: 141, figs 1–3.
Identification. Shell subcylindrical. Spire tall, slightly tapering, sides nearly parallel (middle whorls). Aperture rather small, subovate, with 6 plicae 1 clearly forked parietal plica, resembling the Greek letter lambda (λ), 1 columellar plica, 1 basal plica, 2 large palatal plicae with 1 small, suprapalatal plica above. Palatal callus strongly developed, connecting palatal plicae. Adult lip slightly thickened within, slightly expanded, with a slight medial sinulus. Last whorl with a crest behind the lip. Umbilicus rimate. Protoconch smooth. Teleoconch sculpture weak, irregular, incremental striae. Shell translucent and nearly colourless or waxy white. Height 1.6–1.9 mm (higher than wide).
Recognized from other Gastrocopta species by the combination of its size, nearly cylindrical form, and forked parietal lamella.
Habitat. Forests, alvars, cliffs, sandy savannas, dry grasslands, wooded shoreline, and Great Lakes dunes. Under rocks and dead wood, and in leaf litter. Usually associated with limestone and calcium-rich habitats.
Canadian range. South-eastern British Columbia: near Canal Flats, Columbia Lake. Alberta. (Expected for Saskatchewan). Manitoba: Interlake region and south. Ontario: south and east of Manitoulin Island, expected for the Rainy River District. South-western Quebec: Gatineau hills.
Remarks. Pilsbry (1948) recognized the subspecies, G. holzingeri agna, described from Colorado (Pilsbry & Vanatta 1907). Hubricht (1985) regarded this taxon as a synonym of G. holzingeri but gave no reasons. However, no subspecies are currently recognized.