Freshwater limpets

Code KG069999

Class Gastropoda: Subclass Pulmonata: Order Basommatophora.

A cosmopolitan family of limpet-like snails, without shell coiling. Three Australian species are described in two genera, and the distribution is widespread. Ancylids occur in a variety of freshwaters but are rarely abundant and often overlooked by collectors because of their small size and habit of clinging to the underside of rocks and vegetation.

There is a single Tasmanian species in family Planorbidae that is superficially ancylid-like, but it has a vestige of coiling at the apex of the shell. Otherwise, identification of ancylids to family level should be trouble-free.

The Australian fauna comprises two genera, Ferrisia and Stimulator . The former contains two species, separated on the relative height and size of the shell, and variation in presence of pigment. The latter is known from a single species in far north-west Western Australia. The posterior shell margin may develop a septum or shelf - a horizontal outgrowth that may deverlop enough to resemble a cap on the shell. Although this has been treated as of specific significance, the development appears to be ecologically induced and not taxonomically significant.

Reference:

Smith, B.J. (1996) Identification keys to the Families and Genera of Bivalve and Gastropod Molluscs found in Australian Inland Waters . Cooperative Research Centre for Freshwater Ecology Identification Guide No. 6., Albury, NSW.