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Several populations belonging to the genus Staurosirella have been observed in European rivers that were previously identified as Staurosirella pinnata. In light of the recent taxonomic revisions of the genus Staurosirella, the morphology of the unknown Staurosirella populations has been critically investigated using light and scanning electron microscopy. Following the comparison with previously described Staurosirella species, five taxa could not be identified using the currently available literature on the genus. These five taxa are described as new based on differences in valve outline; shape, size and structure of the apical pore fields; structure of the striae; and the presence, position and structure of the marginal spines. Two new species were described using historic collection material: Staurosirella binodiformis sp. nov. and Svanheurckiana sp. nov. Two new species were observed in samples from rivers in Flanders: S. marginostriata sp. nov. and S. stoksiana sp. nov. whereas a fifth species was observed in rivers from Iceland: S. jonssoniana sp. nov. All new species are compared with similar Staurosirella species worldwide. Notes are added on their ecological preferences derived from both physicochemical data and the associated diatom flora. [ABSTRACT FROM AUTHOR]

During a survey of the marine benthic diatom flora on the coasts off Livingston Island (South Shetland Islands, Maritime Antarctic Region), two Halamphora species that could not be identified based on the currently available literature, were observed. Detailed light and scanning electron microscopy observations and thorough comparison with similar taxa in the literature revealed that both taxa should be described as new species. The first taxon, Halamphora kenderoviana sp. nov., was most likely misidentified in past Antarctic studies, and included within the range of another taxon, Halamphora coffeaeformis. Analysis of literature data showed that the second new taxon, Halamphora moncheviana sp. nov., has been previously reported from the Antarctic Continent (but as an unidentified species). The new taxa are compared with similar Halamphora taxa worldwide. Data on their ecology and distribution are also provided. [ABSTRACT FROM AUTHOR]