Mammillaria pottsii
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Mammillaria pottsii, also known as fox-tail cactus or rat-tail nipple cactus, is a species of flowering plant in the Cactaceae family. It was first described by Scheer ex Salm-Dyck, Cact. Hort. 1849: 104 (1850) According to the United Nations Environment Programme, M. leona is a synonym for M. pottsii.