Abstract
Two new species of the genus Lacustriella from Lake Baikal have been studied by light and scanning electron microscopy. These are Lacustriella concinna and L. provecta, both of which have a unique combination of characters. We document morphological differences between new species and similar Lacustriella taxa; the lacking details on the ultrastructure of the closely related Lacustriella acutocuneata, were supplemented with our own SEM data and used for comparison. Most of the world’s Lacustriella species are currently found in the lake.