, the Creeping Ancylid, in either of its ecophenotypical forms (see below), is widely distributed across North America (Basch, 1963; Burch et al, 1980). It is found across southern British Columbia from the Kootenays to Vancouver Island (Canadian Museum of Nature Collections; Royal BC Museum Collections).
Using molecular methods, Walther et al. (2010) showed that Ferrissia rivularis and Ferrissia parallela represent lotic and lentic ecophenotypes respectively of the same limpet species - with the name Ferrissia rivularis (Say, 1817) having priority over Ferrissia parallela (Haldemann, 1841).
The typically lotic ecophenotype is found attached to rocks and mussel shells in rivers and streams, and attached to rocks in exposed habitats in lakes. The typically lentic ecophenotype is found on vegetation in lakes, swamps, and slow-flowing rivers. It is often found on the stems of cattails and sedges, and on the undersides of lily pads (Clarke, 1981).
Note Author: Ian Gardiner.