Gomphonema acuminatum var. nasuta (Ehrenberg) Prochazka, 1923 accepted as Gomphonema nasutum Ehrenberg, 1843 (new combination reference)
Hantzschia dianae (Ehrenberg) Prochazka, 1923 accepted as Eunotia dianae Ehrenberg, 1840 (new combination reference)
Meridion circulare var. bicapitata (Schonfeldt) Prochazka, 1923 accepted as Meridion constrictum var. bicapitata Schonfeldt, 1913 (new combination reference)
Navicula affinis f. minor (Cleve) Prochazka, 1923 (new combination reference)
Navicula affinis var. longiceps (Gregory) Prochazka, 1923 accepted as Navicula longiceps var. longiceps Gregory, 1856 (new combination reference)
Navicula divergens f. major Zacharias ex Prochazka, 1923 (original description)
Navicula genuflexa var. semicruciata Prochazka, 1923 (original description)
Navicula gracillima var. curta Prochazka, 1923 (original description)
Navicula interrupta var. hybrida (Grunow ex Hofmann) Prochazka, 1923 (new combination reference)
Navicula lata var. pachyptera (Ehrenberg) Prochazka, 1923 accepted as Pinnularia pachyptera Ehrenberg, 1843 (new combination reference)
Navicula lata var. rabenhorstii (Grunow) Prochazka, 1923 accepted as Navicula rabenhorstii var. rabenhorstii Grunow, 1860 (new combination reference)
Navicula microstauron var. biundulata (Otto Müller) Prochazka, 1923 accepted as Pinnularia microstauron f. biundulata (O.Müller) Hustedt, 1930 (new combination reference)
Navicula microstauron var. ornata (Otto Müller) Prochazka, 1923 (new combination reference)
Navicula microstauron var. semicruciata (Otto Müller) Prochazka, 1923 (new combination reference)
Navicula paucicostata (Rabenhorst) Prochazka, 1923 accepted as Stauroptera paucicostata Rabenhorst, 1853 (new combination reference)
Navicula producta var. constricta (Hustedt) Prochazka, 1923 (new combination reference)
Navicula silicula var. genuina (Cleve) Prochazka, 1923 accepted as Caloneis silicula var. genuina Cleve, 1894 (new combination reference)
Navicula silicula var. inflata (Grunow) Prochazka, 1923 accepted as Navicula limosa var. inflata Grunow, 1860 (new combination reference)
Navicula silicula var. kjellmanniana (Cleve in Cleve & Grunow) Prochazka, 1923 (new combination reference)
Navicula silicula var. linearis (Grunow) Prochazka, 1923 accepted as Navicula linearis Grunow, 1860 (new combination reference)
Navicula silicula var. minuta (Grunow) Prochazka, 1923 accepted as Navicula ventricosa var. minuta Cleve & Möller, 1879 (new combination reference)
Navicula silicula var. truncatula (Grunow) Prochazka, 1923 accepted as Navicula ventricosa var. truncatula Grunow, 1880 (new combination reference)
Navicula silicula var. tumida (Hustedt) Prochazka, 1923 accepted as Caloneis silicula f. tumida Hustedt, 1909 (new combination reference)
Navicula silicula var. undulata (Grunow) Prochazka, 1923 accepted as Navicula limosa f. limosa Kützing, 1844 (new combination reference)
Navicula silicula var. ventricosa (Ehrenberg) Frenguelli, 1923 accepted as Navicula ventricosa var. ventricosa Ehrenberg, 1830 (new combination reference)
Navicula stauroptera var. mesogongyla (Ehrenberg) Prochazka, 1923 (new combination reference)
Navicula subcapitata var. subundulata (Otto Müller) Prochazka, 1923 (new combination reference)
Navicula viridis var. interrupta (Hustedt) Prochazka, 1923 accepted as Pinnularia viridis var. interrupta Hustedt, 1914 (new combination reference)
Odontidium hiemale var. minor (Rabenhorst) Proschazka, 1923 (new combination reference)
Odontidium hiemale var. rotundata (Rabenhorst) Proschazka, 1923 accepted as Odontidium rotundatum Rabenhorst, 1853 (new combination reference)
Stauroneis obtusa f. parva Grunow ex Prochazka, 1923 (original description)
Tryblionella tryblionella f. levidensis (W. Smith) Prochazka, 1923 accepted as Tryblionella levidensis W.Smith, 1856 (new combination reference)
Tryblionella tryblionella var. calida (Grunow in Cleve & Grunow; Grunow in Van Heurck) Prochazka, 1923 (new combination reference)
Tryblionella tryblionella var. tryblionella (Hantzsch in Rabenhorst) Prochazka, 1923 accepted as Nitzschia tryblionella f. tryblionella Hantzsch in Rabenhorst, 1860 (new combination reference)