Achnanthes exigua var. constricta (Torka) Hustedt, 1930 accepted as Cocconeis exigua var. constricta Torka, 1909 (original description)
Achnanthes subhudsonis var. subhudsonis Hustedt, 1921 (original description)
Amphora schroederi Hustedt, 1921 (original description)
Anomoeoneis serians f. minor Hustedt, 1921 (original description)
Caloneis aequatorialis Hustedt, 1921 (original description)
Caloneis aequatorialis var. capitata Hustedt, 1921 (original description)
Eunotia pectinalis f. incisa Hustedt, 1921 (original description)
Fragilaria construens var. exigua (W.Smith) Hustedt, 1921 accepted as Triceratium exiguum W.Smith, 1856 (new combination reference)
Hantzschia amphioxys f. africana Hustedt, 1921 (original description)
Hantzschia amphioxys var. distincte-punctata Hustedt, 1921 (original description)
Navicula kwamkuji Hustedt, 1922 (original description)
Navicula lagerheimii sensu Hustedt, 1921 (original description)
Neidium inconspicuum Hustedt, 1921 (original description)
Nitzschia lacustris Hustedt in A. Schmidt, 1922 (original description)
Pinnularia amaniensis Hustedt, 1921 (original description)
Pinnularia divergens f. minor Hustedt, 1921 (original description)
Pinnularia hartleyana f. linearis Hustedt, 1921 (original description)
Stauroneis scaphulaeformis Hustedt, 1921 (original description)
Stauroneis scaphulaeformis f. minor Hustedt, 1921 (1922) (original description)