Studies on the diatom genusNaviculaBory.Navicula scopulorumBréb. and a further comment on the genusBerkeleyagrev.

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Abstract
Two epipelic diatoms with contrasting chloroplast morphology were found, which on the basis of valve morphology and the limited criteria available for specific determinations, could fall into one species, Navicula scopulorum Bréb. Investigation using electron microscopy revealed a number of structural differences on which they could be separated, in addition to their chloroplast morphology and to small differences in valve shape and striation visible with light microscopy. Comparison with type material of N. scopulorum Bréb. showed that one was genuine N. scopulorum, the other, which agreed with Okedenia scopulorum Mereschk. must be placed elsewhere. Some representatives of N. scopulorum had previously been placed in Berkeleya Grev. as B. micans (Lyngb.) Grun. Examination of the type material of the latter revealed the mistaken identification, but as N. scopulorum agreed in all salient features with other species of Berkeleya, it has been transferred to this genus as B. scopulorum (Bréb.) Cox comb. nov. Emended descriptions of B. micans and B. scopulorum are given. The importance of chloroplast studies and the need to use as many characters as possible in any taxonomic investigation are stressed.