Pediocactus simpsonii is also refered to as Mountain Cactus. The plants grow at a high elevation and are found from Montana to northern Arizona.

The flower colour is usually pale pink to pale yellow.

Pediocactus simpsonii in cultivation. An interesting dark pink flowering form.
(Photograph edited to remove blemishes.)

Pediocactus knowltonii is endemic to a few counties of New Mexico. It is a rare species and often confined to small areas.

Pediocactus knowltonii in cultivation