Some freshwater and brackish water species of the diatom genus Thalassiosira Cleve

Twelve freshwater and/or brackish water species of the generally regarded marine planktonic diatom genus Thalassiosira are known. The morphology based on light and electron microscopy, taxonomy, and distribution of six of them are discussed. The new combinations Thalassiosira faurii (Gasse) Hasle and T. rudolfii (Bachmann) Hasle are proposed, and T. guillardil sp. nov. including Guillard's clone 7–15 is described. While the areola array is of the same type, the process pattern of these species, particularly number of labiate processes and number and arrangement of central strutted processes, varies greatly.