Abstract
Two rheophilic diatoms, Achnanthes convergens H. Kos. and A. japonica H. KOB. described in 1965 from the Ara-Kawa ( Ara River ) without type citation by one of the present authors, H. KOBAYASI, were re-examined in detail with SEM and TEM using original materials. In addition to the results obtained by careful comparison with the type slides of the related species, morphological differences of these species are confirmed and types are designated, thereby validating these previously invalid names.
