Asteromphalus ingens Simonsen, 1974 (original description)
Bacteriastrum furcatum var. hispida (Castracane) Simonsen, 1974 accepted as Bacteriastrum wallichii var. hispida Castracane, 1886 (new combination reference)
Coscinodiscus concinniformis Simonsen, 1974 (original description)
Coscinodiscus concinnoides Simonsen, 1974 (original description)
Coscinodiscus nobilis Grunow, 1879 (original description)
Coscinodiscus plicatoides Simonsen, 1974 (original description)
Cymatonitzschia R. Simonsen, 1974 (original description)
Cymatonitzschia marina (Lewis) Simonsen, 1974 accepted as Cymatopleura marina Lewis, 1862 (new combination reference)
Cymatonitzschia shulzei (Boyer) Simonsen, 1974 accepted as Cymatopleura shulzei C.S. Boyer, 1909 (new combination reference)
Glyphodesmis rhombica (Cleve) Simonsen, 1975 accepted as Fragilaria rhombica Cleve, 1901 (new combination reference)
Haslea R. Simonsen, 1974 (original description)
Haslea crucigera (W.Smith) Simonsen, 1974 accepted as Schizonema cruciger f. cruciger W. Smith, 1856 (new combination reference)
Haslea crucigeroides (Hustedt) Simonsen, 1974 (new combination reference)
Haslea crystallina (Hustedt) Simonsen, 1974 accepted as Navicula crystallina Hustedt, 1961 (new combination reference)
Haslea frauenfeldii (Grunow) Simonsen, 1974 accepted as Amphipleura frauenfeldii Grunow, 1863 (new combination reference)
Haslea gigantea (Hustedt) Simonsen, 1974 accepted as Navicula gigantea Hustedt, 1961 (new combination reference)
Haslea gretharum Simonsen, 1974 (original description)
Haslea hyalinissima Simonsen, 1974 (original description)
Haslea kjelmanii (Cleve) Simonsen, 1974 (new combination reference)
Haslea ostrearia (Gaillon) Simonsen, 1974 accepted as Vibrio ostrearius Gaillon, 1820 (new combination reference)
Haslea sulcata (Cleve) Simonsen, 1974 accepted as Stauroneis sulcata Cleve, 1881 (new combination reference)
Haslea trompii (Cleve) Simonsen, 1974 accepted as Navicula trompii var. trompii Cleve, 1900 (new combination reference)
Haslea vitrea (Cleve) Simonsen, 1974 accepted as Pleurosigma vitrea var. vitrea Cleve in Cleve & Moller, 1879 (new combination reference)
Haslea wawrikae (Hustedt) Simonsen, 1974 (new combination reference)
Navicula distantepunctata Simonsen, 1974 (original description)
Navicula gretharum Simonsen, 1974 (original description)
Nitzschia capuluspalae Simonsen, 1965 (original description)
Nitzschia dietrichii Simonsen, 1974 (original description)
Nitzschia inflatula var. capitata Simonsen, 1974 (original description)
Nitzschia interruptestriata Simonsen, 1974 (original description)
Nitzschia ossiformis (Taylor) Simonsen, 1974 accepted as Synedra ossiformis Taylor, 1967 (new combination reference)
Odontella regia (Schultze) Simonsen, 1974 (new combination reference)
Pachyneis R. Simonsen, 1974 (original description)
Pachyneis gerlachii Simonsen, 1974 (original description)
Pinnularia cuneatoundulata Simonsen, 1974 (original description)
Pleurosigma indicum Simonsen, 1974 (original description)
Pleurosigma planctonicum R.Simonsen, 1974 (original description)
Porosira denticulata Simonsen, 1974 (original description)
Pseudotriceratium punctatum (Wallich) Simonsen, 1974 accepted as Triceratium punctatum Wallich, 1860 (new combination reference)
Rhaphoneis surirelloides Simonsen, 1974 (original description)
Thalassiosira punctifera (Grunow) Fryxell, Simonsen & Hasle, 1974 accepted as Coscinodiscus excentricus var. punctifera Grunow, 1884 (new combination reference)
Thalassiosira spinosa Simonsen, 1974 (original description)
Trigonium reticulum (Ehrenberg) Simonsen, 1974 accepted as Triceratium reticulum f. reticulum Ehrenberg, 1844 (new combination reference)
Tropidoneis subulata Simonsen, 1974 accepted as Phycostilus subulatus (Simonsen) Blanco, 2020 (original description)