Abstract
A new species and a new variety belonging to the diatom genus Navicula are described from a high-altitude lake in Tibet, China. Both taxa were studied under light and scanning electron microscopy. Comparisons with morphologically similar taxa are provided. Navicula gololobovae sp. nov. resembles N. schweigeri, N. capitatoradiata, N. subalpina, N. krammeriae and N. arkona. Navicula cryptofallax var. tibetica var. nov. is compared with the nominate variety of the species and N. cryptocephala. The unique sets of morphological characters observed in our new taxa allow their unambiguous separation from similar taxa.