A review of some species of **Berkella** and **Frustulia** occurring in freshwaters of Britain and Ireland with documentation of the types of **Berkella linearis**, **B. alpina**, **Frustulia saxonica** and **F. crassinervia** University of Antwerp
We investigated the type material ofBerkella linearis, B. alpina, Frustulia saxonica, and F. crassinervia, and populations of these taxa and of F. vulgaris, F. quadrisinuata, F. erifuga, and F. amphipleuroides from Scotland and Wales with light and scanning electron microscopy. The spe-cies are distinguished from each other in light microscopy by differences in the shape of the valves, apices and central areas, and in scanning electron ...