Trochus australis Philippi Monodonta australis, common name the toothed topshell, is a species of sea snail, a marine gastropod mollusk in the family Trochidae, the top snails.

The shell is similar to Monodonta labio, but with rounder whorls, more marked sutures and with lower lirae.

The penultimate whorl is subangulate by the prominence of its central rib.

The columella is much less strongly dentate than in Monodonta labio, and the notch or canal below it shallow.

[2] This marine species occurs off South Africa and in the Indian Ocean off Madagascar, Aldabra and the Mascarene Basin; also off Japan.