Mammillaria schiedeana ssp. schiedeana
This delightful cactus is native to Mexico. It can grow as a solitary stem or in clumps, and has white flowers in Winter. The individual stems can reach a height of 10 cm and width of 6cm. It prefers a sunny position in well-draining soil, but should be protected from extreme heat. Watering regular in Summer, allowing it to dry out between waterings, and keep dry in Winter.