Cropped.

Thus is Pediocactus simpsonii, commonly called Simpson Hedgehog Cactus or Mountain Ball Cactus. It has a range in a American West from Oregon to Montana and southwards into New Mexico. The cactus is still relatively uncommon, growing in high elevation locations, often in small, localized areas, frequently obscured by grass and fallen leaves.
This is one of two growing in my front yard cactus garden and is an early bloomer.