Notocactus ottonis var. megapotamicus (Osten ex Herter) Buining in Succulenta (Netherlands) 1957: 108. 1957 Notocactus ottonis var. megapotamicus (Osten ex Herter) Buining in Succulenta (Netherlands) 1957: 108. 1957Taxon for this nameNotocactus ottonis var. megapotamicus (Osten ex Herter) Buining
