Spanning a large latitudinal range (N34°25'–49°10'), the diatom flora of the Xinjiang
Uygur Autonomous Region includes both cold and temperate diatom taxa, as well as some unique taxa adapted to alkaline or alpine conditions. We collected diatoms from 311 sites distributed in representative water bodies throughout Xinjiang, at altitudes between 450–3600 m and with pH between 7.0–10.5. Fourteen Epithemia taxa and eleven Rhopalodia taxa are identified, including one new species (Epithemia arguiformis). Synonyms, references, morphological characters, remarks, and ecological affinities are given for each taxon. Some taxa for which we could not find any description are also presented with detailed descriptions and images. Besides a detailed description, each taxon is depicted with one or more microphotographs; in addition, a number of SEM images are presented. The analysis shows that the distribution of the genera Epithemia and Rhopalodia varied strongly between different ecological habitats, and also has different trends among the three main regions in Xinjiang.