Abstract
A member of the Chrysophyceae, Mallomonopsis tasmanica, is described from a dystrophic, meromictic lake in Tasmania as a new species. It is recognized by possession of two flagella, scale morphology and bristle type. It is a strong swimmer and during the day apparently occupies a discrete stratum in the water column. The occurrence of Mallomonopsis elliptica Matvienko is reported from tropical Australia. In both species bristle morphology varies considerably.