Genus Isidora, Ehrenberg (1831).

Synonyms: Diastropha, Gray (1840); Ameria, H. Adams (1861); Glyptophysa, Crosse (1872); Pyrgophysa, Crosse (1879); Physastra, Tapparone Canefri (1883).

Animal without the produced and reflected mantle-lobes of Physa; radula Limnæidian, approaching Planorbis rather than Limnœa; central tooth bicuspid, cusps rather blunt, base square; laterals tricuspid; marginals serrate. Laterals about 6–10, marginals about 25–33. Number of rows varying between 140 and 220.

Shell sinistral, resembling that of Physa, acuminated or gibbous, smooth or keeled; texture somewhat thick, covered with a deciduous epidermis; columella strong, often reflected, umbilicus sometimes very wide and deep.

Distribution: Australia, Tasmania, New Zealand, New Guinea, New Caledonia, Fiji, Tonga, Africa (north, north-east, west, and south), southern France, Spain, and all countries bordering the Mediterranean.

Ameria was proposed for Physœ with keeled whorls. The