Thelocactus bicolor (Galeotti ex Pfeiff.) Britton & Rose Thelocactus bicolor (Galeotti ex Pfeiff.) Britton & Rose in Bull. Torrey Bot. Club 49: 251. 1922 sec. Guzmán & al. 2003≡Echinocactus bicolor Galeotti ex Pfeiff. in Abbild. Beschr. Cact. 2: t. 25. 1848 syn. sec. Guzmán & al. 2003