Achnanthes heterovalvata (Krasske) Frenguelli, 1942 accepted as Achnanthes exigua f. heterovalvata Krasske, 1923 (new combination reference)
Achnanthes heterovalvata var. angustirostrata (Krasske) Frenguelli, 1942 accepted as Achnanthes exigua f. angustirostrata Krasske, 1939 (new combination reference)
Caloneis subpatagonica Frenguelli, 1942 (original description)
Caloneis subpatagonica f. curta Frenguelli, 1942 (original description)
Cocconeis neuquina Frenguelli, 1942 (original description)
Cyclotella stelligera var. elliptica Frenguelli, 1942 accepted as Discostella stelligera var. elliptica (Frenguelli) J.M. Guerrero & R.O Echenique, 2006 (original description)
Cyclotella stipata Frenguelli, 1942 accepted as Guarreraea stipata (Frenguelli) Kociolek & Guerrero in Guerrero et al., 2018 (original description)
Cymbella neuquina Frenguelli, 1942 (original description)
Cymbella rigida Frenguelli, 1942 accepted as Cymbella helvetica Kützing, 1844 (original description)
Diploneis andina Frenguelli, 1942 accepted as Muelleria andina (Frenguelli) Guerrero, Vouilloud & Serino 2024 (original description)
Encyonema patagonicum Frenguelli, 1942 (original description)
Encyonema subturgidum Frenguelli, 1942 (original description)
Eunotia andina Frenguelli, 1942 (original description)
Eunotia polydentula var. ventricosa (M. Peragallo) Frenguelli, 1942 accepted as Eunotia tridentula var. ventricosa M. Peragallo, 1921 (new combination reference)
Fragilaria fonticola f. constricta Frenguelli, 1942 (original description)
Fragilaria fonticola var. subcapitata Frenguelli, 1942 (original description)
Fragilaria fonticola var. tetragona Frenguelli, 1942 (original description)
Gomphonema acuminatum var. spoliata Frenguelli, 1942 (original description)
Gomphonema frickei O.Müller, 1905 (additional source)
Gomphonema frickei Frenguelli, 1923 accepted as Gomphonema frickei O.Müller, 1905 (source of synonymy)
Gomphonema frickei var. andina Frenguelli, 1942 (original description)
Gomphonema navicelloides Frenguelli, 1942 (original description)
Gomphonema subclavatum var. tenella (Kützing) J.Frenguelli, 1942 accepted as Gomphonema tenellum var. tenellum Kützing, 1844 (new combination reference)
Hantzschia amphioxys var. inversa Frenguelli, 1942 (original description)
Hantzschia subandina Frenguelli, 1942 accepted as Nitzschia subandina (Frenguelli) Kociolek & Vouilloud, 2020 (original description)
Navicula andium Frenguelli, 1942 (original description)
Navicula cordillerae Frenguelli, 1942 (original description)
Navicula grimmei var. producta Frenguelli, 1942 (original description)
Navicula grimmii var. producta Frenguelli, 1942 (original description)
Navicula guatemalensis var. minor (Frenguelli) Frenguelli (original description)
Navicula peregrina var. acuta (Mayer) Frenguelli, 1942 (new combination reference)
Navicula pseudocari var. minor Frenguelli, 1942 (original description)
Navicula trolopensis Frenguelli, 1942 (original description)
Neidium affine var. dubia (Ehrenberg) Frenguelli, 1942 accepted as Navicula dubia f. dubia Ehrenberg, 1843 (new combination reference)
Neidium iridis var. vernalis (Reichelt ex Hustedt) Frenguelli, 1942 (new combination reference)
Neidium kozlowi var. rostrata Frenguelli, 1942 (original description)
Nitzschia denticula var. capitata Frenguelli, 1942 (original description)
Nitzschia sublinearis var. major Frenguelli, 1942 (original description)
Pinnularia alpina var. kerguelensis (Heiden & Kolbe) Frenguelli, 1942 accepted as Pinnularia kerguelensis H.Heiden (new combination reference)
Pinnularia andina Frenguelli, 1942 (original description)
Pinnularia aperta f. undulata (Frenguelli) Frenguelli, 1942 accepted as Navicula doeringii var. undulata Frenguelli, 1926 (new combination reference)
Pinnularia aperta var. doellojurandoi (Frenguelli) Frenguelli, 1942 accepted as Navicula doellojuradoi Frenguelli, 1924 (new combination reference)
Pinnularia aperta var. doeringii (Frenguelli) Frenguelli, 1942 accepted as Navicula doeringii var. doeringii Frenguelli, 1923 (new combination reference)
Pinnularia appendiculata var. major Frenguelli, 1942 (original description)
Pinnularia bogotensis var. patagonia Frenguelli, 1942 (original description)
Pinnularia cordillerae Frenguelli, 1942 (original description)
Pinnularia crucicula Frenguelli, 1942 (original description)
Pinnularia delicata Frenguelli, 1942 (original description)
Pinnularia delicatula Frenguelli, 1945 accepted as Pinnularia delicata Frenguelli, 1942 (additional source)
Pinnularia divergens var. subcapitata Frenguelli, 1942 (original description)
Pinnularia elliptica Frenguelli, 1942 accepted as Pinnularia lamaroana Guerrero & Vouilloud, 2021 (original description)
Pinnularia gracilens Frenguelli, 1942 (original description)
Pinnularia gracilens var. gracilens Frenguelli, 1942 (original description)
Pinnularia graciloides var. krasskei Frenguelli, 1942 accepted as Pinnularia lange-bertalotii K.Krammer, 1992 (original description)
Pinnularia neuquina Frenguelli, 1942 (original description)
Pinnularia polyonca sensu Frenguelli, 1942 (original description)
Pinnularia streptoraphe var. subacuta Frenguelli, 1942 (original description)
Stauroneis signata Frenguelli, 1942 accepted as Stauroneis catalanorum Vouilloud, Molinari & Guiry, 2021 (original description)
Surirella linearis f. festetichii (Pantocsek) Frenguelli, 1942 accepted as Surirella festetichii Pantocsek, 1902 (new combination reference)
Surirella ovata var. elliptica Frenguelli, 1942 (original description)
Tryblionella hantzschiana var. levidensis (W.Smith) Frenguelli, 1942 accepted as Tryblionella levidensis W.Smith, 1856 (new combination reference)
Tryblionella hungarica (Grunow) Frenguelli, 1942 accepted as Nitzschia hungarica f. hungarica Grunow, 1862 (new combination reference)
Vanheurckia rhomboides f. marginata (Amossé) Frenguelli, 1942 accepted as Frustulia marginata Amossé, 1932 (new combination reference)
Vanheurckia rhomboides var. elliptica (Hustedt) Frenguelli, 1942 accepted as Frustulia rhomboides var. elliptica Hustedt, 1937 (1938) (new combination reference)
Vanheurckia rhomboides var. lanceolata (Zimmermann) Frenguelli, 1942 accepted as Frustulia lanceolata Zimmermann, 1918 (new combination reference)
Vanheurckia suspecta var. obtusa Frenguelli, 1942 accepted as Frustulia suspecta var. obtusa (Frenguelli) Woodhead & Tweed, 1960 (original description)
Vanheurckia vulgaris var. capitata (Krasske) Frenguelli, 1942 accepted as Frustulia vulgaris var. capitata Krasske, 1923 (new combination reference)

Neuquén for Cyclotella stipata Frenguelli, 1942 
Neuquén for Cyclotella stipata Frenguelli, 1942 
Neuquén for Cymbella rigida Frenguelli, 1942 
Neuquén for Cymbella rigida Frenguelli, 1942 
Neuquén for Diploneis andina Frenguelli, 1942 
Neuquén for Diploneis subovalis var. argentina Frenguelli, 1932 
Neuquén for Encyonema patagonicum Frenguelli, 1942 
Neuquén for Encyonema patagonicum Frenguelli, 1942 
Neuquén for Encyonema subturgidum Frenguelli, 1942 
Neuquén for Eunotia andina Frenguelli, 1942 
Neuquén for Eunotia andina Frenguelli, 1942 
Neuquén for Eunotia andina Frenguelli, 1942 
Neuquén for Fragilaria pinnata var. subcapitata Frenguelli, 1930 
Neuquén for Fragilaria pinnata var. subcapitata Frenguelli, 1930 
Neuquén for Gomphonema frickei var. andina Frenguelli, 1942 
Neuquén for Gomphonema navicelloides Frenguelli, 1942 
Neuquén for Hantzschia amphioxys var. inversa Frenguelli, 1942 
Neuquén for Hantzschia subandina Frenguelli, 1942 
Neuquén for Hantzschia subandina Frenguelli, 1942 
Neuquén for Navicula andium Frenguelli, 1942 
Neuquén for Navicula cordillerae Frenguelli, 1942 
Neuquén for Navicula grimmei var. producta Frenguelli, 1942 
Neuquén for Navicula pseudocari var. minor Frenguelli, 1942 
Neuquén for Navicula pseudocari var. minor Frenguelli, 1942 
Neuquén for Navicula trolopensis Frenguelli, 1942 
Neuquén for Nitzschia sublinearis var. major Frenguelli, 1942 
Neuquén for Nitzschia sublinearis var. major Frenguelli, 1942 
Neuquén for Pinnularia andina Frenguelli, 1942 
Neuquén for Pinnularia cordillerae Frenguelli, 1942 
Neuquén for Pinnularia crucicula Frenguelli, 1942 
Neuquén for Pinnularia crucicula Frenguelli, 1942 
Neuquén for Pinnularia delicata Frenguelli, 1942 
Neuquén for Pinnularia divergens var. subcapitata Frenguelli, 1942 
Neuquén for Pinnularia elliptica Frenguelli, 1942 
Neuquén for Pinnularia neuquina Frenguelli, 1942 
Neuquén for Pinnularia neuquina Frenguelli, 1942 
Neuquén for Pinnularia neuquina Frenguelli, 1942 
Neuquén for Pinnularia neuquina Frenguelli, 1942 
Neuquén for Pinnularia streptoraphe var. subacuta Frenguelli, 1942 
Neuquén for Stauroneis signata Frenguelli, 1942 
Neuquén for Stauroneis signata Frenguelli, 1942 
Neuquén for Surirella ovata var. elliptica Frenguelli, 1942 
Neuquén for Vanheurckia suspecta var. obtusa Frenguelli, 1942 
Neuquén for Vanheurckia suspecta var. obtusa Frenguelli, 1942 
Rio Negro for Cocconeis neuquina Frenguelli, 1942 
Rio Negro for Cymbella neuquina Frenguelli, 1942 
Rio Negro for Fragilaria fonticola var. tetragona Frenguelli, 1942 
Rio Negro for Fragilaria pinnata var. subcapitata Frenguelli, 1930 
Rio Negro for Gomphonema acuminatum var. spoliata Frenguelli, 1942 
Rio Negro for Neidium kozlowi var. rostrata Frenguelli, 1942 
Rio Negro for Nitzschia denticula var. capitata Frenguelli, 1942 
Rio Negro for Pinnularia appendiculata var. major Frenguelli, 1942 
Rio Negro for Pinnularia gracilens Frenguelli, 1942 
Rio Negro for Pinnularia graciloides var. krasskei Frenguelli, 1942