Shells minute, rissoiform, with no anterior canal on aperture; animals subjected to sexual dimorphism. The main distinctive features remain anatomic.
 

« Shell ovate-conic, imperforate; apex acute; whorls coronated with spines; outer whorl nearly two-thirds the length of the shell; aperture ovate, outer lip acute. Operculum corneous, subspiral. » – W. Stimpson: “Diagnoses of newly discovered genera of gasteropods, belonging to the sub-family Hydrobiinae, of the family Rissoidae”, American journal of conchology vol.I, Philadelphia 1865, p.53. But « the extent of morphological variation among the group as a whole is large and distinction of species using these criteria has generally been confused. The extreme morphological variation within P. antipodarum, and the similarities observed between certain forms of this species and other species in the genus, suggest that a technique independent of morphological characters might be of use in inferring relationships. » – Philips & Lambert: “A cladistic analysis of species of the molluscan genus Potamopyrgus based on allozyme data”, New Zealand Journal of Zoology vol.17(2), Wellington 1990, p.257.