Frailea pygmaea var. gloriosa Prestlé

Origin and Habitat: Frailea pygmaea grows widespread over a wide area in Brazil, Uruguay and Argentina.
Habitat & ecology: Grows often in mountainous region in scattered but numerous populations, and it is often quite common. Usually it is found in the crevices of rocky outcrops, between the pebbles near these outcrops or in grassy, gravelly areas where the thin soil depth minimizes any competition from other plants. It is often found growing together with Frailea gracillima and Frailea castanea. The rain fall are quite frequent and often abundant.

Description: Frailea pygmaea as the name implies ("pygmaeus" meaning dwarf), is a very small cactus that lives half buried in the ground. globose. Most of the plants in habitat are single headed unless they are damaged. It is extremely an variable species with many different form
The gloriosa form is very nice, due to it long white spines.
Flowers: up to 3 cm diameter, pale yellow, with dense, whitish to rose-colored
Blooming season: Hottest part of summer.

Cultivation and Propagation: Grow them in rich, porous soil and let them dry out between waterings. These plants need a minimum temperature of 5-10° C (but occasionally temperatures of a few degrees below 0° are not dangerous)
Sun Exposure: They enjoy full sun but in a shaded position the plants grow faster, but are not flat shaped.
Characteristically, during the dry season plants retract completely under the ground both in the wild and in cultivation too.

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