Rapicactus booleanus

Rapicactus booleanus is a species of plant in the family Cactaceae.

Description
Rapicactus booleanus grows solitarily with a tuberous root connected to the stem by a narrow neck 1 - 5 cm long. The grey-green stems are spherical, obovate to turbinate, narrowing at the collar, and measure 2.5 - 4.5 cm tall and 2.5 - 5.5 cm in diameter. The hard, spirally arranged tubercles are closely set, 4-angled, rhomboid, somewhat flattened and almost truncated above, and somewhat horny or keeled below. There are 2 erect central spines, whitish with dark brown tips, measuring 12 - 21 mm long. Around 18-20 radial spines are white and measure 3 - 17 mm long. Flowers are pale to dark magenta with darker midstripes, blooming on summer days, and are 2 cm long and 2.5 cm in diameter. The fruits are dark green to purple, measure 7 mm long and 6 mm in diameter, and split open when ripe.

Distribution
Plants are found growing in gypsum outcrops near San Roberto, Nuevo León and in general Mexico.