Acanthocalycium ferrarii
Acanthocalycium klimpelianum
Acanthocalycium spiniflorum

Acanthocalycium (Backeberg 1935) is a genus of cacti consisting of three species from Argentina. The name akantha, prickly, + kalyx buds, refers to the spines on the floral tubes.

The plants are globose to elongate, with numerous ribs on the spiny stems. Flowers range from white to pink to red, and open during the day.

Acanthocalycium species have been periodically considered part of Echinopsis.

Reference

• Edward F. Anderson , The Cactus Family (Timber Press, 2001), pp. 105-106