Abstract
Two taxa presented by Ehrenberg as belonging to the genera Sphaerotermia Ehrenberg and Gaillonella Bory, Sphaerotermia horologium Ehrenberg and Gaillonella californica from mica-strips of the Ehrenberg Collection deposited at the Natural History Museum, Humboldt University of Berlin (Germany), were observed and investigated in the light microscope (LM) to show their LM morphologies, with a higher resolution than those of Ehrenberg's, and possible clarification of their taxonomy. Raw materials from the respective mica-strips were also observed, but no diatoms were found. The observed valve morphologies of these taxa are discussed and compared with those of closely related taxa and two new combinations, Miosira horologium (Ehrenberg) comb. nov. and Aulacoseira californica (Ehrenberg) comb, nov., are suggested.