Mammillaria guillauminiana Backeb. Mammillaria guillauminiana Backeb. in Cactus (Paris) 33: 81-82. 1952 sec. Hunt 2016=Mammillaria mercadensis var. guillauminiana (Backeb.) Repp., Gatt. Mammillaria: 3. 1987 syn. sec. Guzmán & al. 2003