Coryphanta greenwoodii

A common name is Elephants Tooth.

Cultivation and propagation: Full sun to light shade in summer. Water sparingly, keep drier in winter. Needs good drainage.

Frost tolerance: Hardy to -3°C.

The flower is yellow.

Some of the information in this description has been found at desert-tropicals.com, llifle.com and cactus-art.biz