Melocactus jansenianus Backeb. in Blätt. Kakteenf. 1935(2): 2. 1935 Melocactus jansenianus Backeb. in Blätt. Kakteenf. 1935(2): 2. 1935is basionym for Cactus jansenianus (Backeb.) Borg, Cacti, ed. 1: 279. 1937Taxon for this nameMelocactus jansenianus Backeb.