The typically showy flowers of this genus are yellow, often with a red center, and to 6 cm or more across. In this species there is the added attraction of bold spination. Each conical tubercle is armed, as the botanical epithet implies, with three, stout, dark-tipped, recurved, dagger-like spines. The species is known only from the area around San Juan Capistrano, Zacatecas, Mexico, at about 300 m above sea level. HBG 104729. $7.