Results from our investigation of Upper Cretaceous diatoms from the Marca Shale Member of the Moreno Shale in California and from Ocean Drilling Program (ODP) Hole 748C on the Kerguelen Plateau, Southern Indian Ocean enable a clarification of the taxonomic position of several diatoms. Differences in areola structure, a primary and conservative character of the diatom valve, are used to separate diatoms recently included in the genus Benetorus. We resurrect the genus Pomphodiscus to include species with locular areolae, a central rimoportula, and a central inflated chamber. We propose the new species Pomphodiscus kerguelensis n. sp. and new combination Pomphodiscus craspedodiscoides comb. nov.