Abstract
Cymbella (Encyonema) grossestriata var. recta Frenguelli (1938: 303) was described by Joaquín Frenguelli (1883–1958) from the Matanza river estuary in Buenos Aires, Argentina. It was subsequently transferred to the genus Navicula Bory (1822b: 128) by Metzeltin et al. (2005: 138), who elevated Frenguelli’s variety to species level. The authors provided evidence that the taxon was not related to Cymbella grossestriata O. Müller (1905: 154) and did not belong to either Cymbella C.A. Agardh (1830: 1) or Encyonema Kützing (1833: 589).