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 (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 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)
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 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 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 divergens var. subcapitata Frenguelli, 1942 (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)
Surirella linearis f. festetichii (Pantocsek) Frenguelli, 1942 accepted as Surirella festetichii Pantocsek, 1902 (new combination reference)
Tryblionella hungarica (Grunow) Frenguelli, 1942 accepted as Nitzschia hungarica f. hungarica Grunow, 1862 (new combination reference)