Achnanthes semifasciata (Østrup) M. Møller in Foged, 1974 accepted as Navicula semifasciata Østrup, 1918 (new combination reference)
Caloneis frigida Foged, 1974 (original description)
Cymbella behrei Foged, 1974 accepted as Encyonopsis behrei (Foged) Krammer & Metzeltin in Krammer, 1997 (original description)
Cymbella prostrata var. caespitosa (Kützing) Foged, 1974 accepted as Encyonema caespitosum Kützing, 1849 (new combination reference)
Cymbella schwabei Foged, 1974 (original description)
Fragilaria construens f. borealis Foged, 1974 (original description)
Navicula explanata var. lanceolata Foged, 1974 (original description)
Navicula stephanssoni Foged, 1974 (original description)
Navicula thoroddseni Foged, 1974 (original description)
Neidium affine f. incurvum (Gregory, Ostrup) Foged, 1974 (new combination reference)
Neidium affine f. incurvum (Gregory) Foged, 1974 accepted as Navicula incurva f. incurva Gregory, 1856 (new combination reference)
Pinnularia cruciformis f. capitata Foged, 1974 (original description)
Pinnularia esox var. islandica Foged, 1974 (original description)
Pinnularia kriegeriana f. undulata Foged, 1974 accepted as Pulchellophycus undulatus (Foged) Edlund & M.J.Wynne, 2019 (original description)
Surirella turgida f. obtusa Foged, 1974 (original description)