About Mammillaria pottsii Scheer ex Salm-Dyck
Mammillaria pottsii, commonly called fox-tail cactus or rat-tail nipple cactus, is a species of flowering plant in the cactus family Cactaceae. It was first formally published by Scheer ex Salm-Dyck in the work Cact. Hort. 1849: 104, which was released in 1850. Per the United Nations Environment Programme, Mammillaria leona is recognized as a synonym of Mammillaria pottsii.