2001 Volume 17 Pages 3-19
Recently Paradiadesmis proves as a moderately species-rich subgenus whereas the nominate subgenus of Diadesmis contains, so far known, very few taxa, all similar to the type species, Diadesmis confervacea. Diadesmis fukushimae, Diadesmis tahitiensis, Diadesmis virginiana and Diadesmis paracontenta ssp. magisconcava are proposed as new taxa. Two other probably new taxa, both from French Polynesia, are discussed and shown by SEM or LM and SEM microphotographs respectively. Diadesmis biscutella, known up to now only from New Caledonia (Melanesian Islands), is identified also in two Polynesian islands. The frustules display heterovalvy here facultatively. Diadesmis irata and D. brekkaensis, two commonly misidentified taxa, are shown as distinctly independent species. The holotype of the latter is photographed for the first time and compared with conspecific populations from Central Europe and Central America. Seven other established, but in parts rarely recorded Diadesmis taxa are shown by SEM-photographs for comparison and better identification.
