Escobaria minima

Pelecyphora minima (syn. Coryphantha minima, Escobaria minima) is a rare species of cactus known by the common names Nellie cory cactus, Nellie's pincushion cactus, birdfoot cactus, and others. It is a very popular species among cactus collectors. This is one reason why it is a highly endangered species in the wild today. This cactus is found only in Brewster County, Texas, in the United States, where there are three populations remaining near Marathon. The cactus is limited to one outcrop in the Marathon Uplift, where it grows in rocky novaculite soils. It was added to the endangered species list in 1979....read more on Wikipedia.