Mammillaria albicans
Origin and habitat: Baja California Mexico.
Habit: Solitary or clustering cylindrical cactus entirely hidden under the many closely set spines.
Mammillaria albicans produces clumps of 5-15 branches with cylindrical stems closely crowded and obscured by spines . Areoles densely white-woolly in youth.
Flowers: Around the top, white to pale pink, with pinkish mid-veins, up to 20 mm in diameter. Outer perianth-segments with a pinkish mid-rib. Inner perianth-segments white. Filaments pinkish. Style nearly white; stigma-lobes nearly white to purplish.
Blooming season: Summer (June to August).
Some of the information in this description has been found at desert-tropicals.com, llifle.com and cactus-art.biz