Abstract
During a revision of the genus Fragilaria in Europe, two unknown Fragilaria taxa were observed in Erken Lake, Sweden, that showed some resemblance to Fragilaria perminuta, a species described in the nineteenth century from the Great Lakes in the United States. The type material of Synedra perminuta from Lake Erie, U.S.A. (Grunow sample 2592) was analysed. Detailed morphological analysis, using both light and scanning electron microscope observations and comparison with the type material, showed that both taxa from Sweden should be described as new species: Fragilaria goeyersiana sp. nov. and F. vandevondeliana sp. nov. The separation of the two taxa is based on valve outline, shape of the apices and stria density. Comparisons are made with similar taxa and brief notes on their ecology are added.