It is a small kind of cactus, forming a flattened and strongly ribbed sphere.
Flowers: 1-5 gathered together at the top, bright yellow, funnel-shaped, large, about 5-8 cm across. The outer perianth-lobules are narrow, sharp, reddish, the inner perianth-lobules are oblong, yellow, almost transparent, except for reddish tips, sharp. The stigma-petals are scarlet. The scales on the ovary are hairy in the sinuses. The perianth is a thin tube.