Abstract
P. pienaarii and P. simplex share the common feature of lacking obvious flagella during the palmelloid stage, in contrast to the type-species P. pigra Geitler. Both species are mainly distinguished by the fine structure of 2 types of body scales: flat inner scales arranged in several layers and a single outer layer of cup-scales with straight up-standing rims. In P. pienaarii the outer scales are characterized by radial ingrowths which are absent in the other species. The main ultrastructural features of the cells are described.