Echinocactus horizonthalonius subsp. nicholii (L.D.Benson) U.Guzmán in Cactaceae Syst. Init. 16: 17. 2003
Echinocactus horizonthalonius subsp. nicholii in Cactaceae Syst. Init. 16: 17. 2003
is new combination for Echinocactus horizonthalonius var. nicholii, Cacti Ariz., ed. 3: 23. 1969