Аннотация:A new monotypic diatom genus from Laos is described, Okhapkinia alexandrii Glushchenko, Kulikovskiy
& Kociolek gen. et sp. nov. The new genus is described on the basis light and scanning electron microscope observations. This genus is similar morphologically to the genus Sellaphora Mereschkowsky on the basis of several shared features. These features include presence of uniseriate striae, internal hymenate pore occlusions, large, elongate helictoglossae, round depressions at the valve face mantle junction, straight internal raphe slit, presence of longitudinal lines positioned on either side of the axial area, and striae arrangement and shape. The new genus is diagnosed by having an external, undulate raphe slit, absence of polar bars, presence of massive basal siliceous layer, and presence of rims and external thickenings around the areolae, central raphe ends curved to different sides internally and very prominent elongated hymenes internally. In all of these features the new genus differs from Sellaphora. The shared features between Okhapkinia gen. nov. and Sellaphora suggest the new genus should be assigned to the Sellaphoraceae Mereschkowsky. Similarites between Okhapkinia gen. nov. and other newly-described genera are discussed. We consider the newly described genus Altana Kulikovskiy, Lange-Bertalot & Metzeltin, which shares the feature of external silica outgrowths with Okhapkinia gen. nov. to be part of the family Cavinulaceae D.G. Mann. The genus Buryatia Kulikovskiy, Lange-Bertalot & Metzeltin described from Lake Baikal may represent another genus closely related to Sellaphora, and suggest it is also a member of the family Sellaphoraceae.