⚠ Version 1 of The Plant List has been superseded.
This name is in version 1.1 of The Plant List, record kew-2781903, and has not been changed.
This name is a synonym of Echinocactus horizonthalonius subsp. nicholii (L.D.Benson) U.Guzmán.
The record derives from WCSP (in review) which reports it as a synonym with original publication details: Cacti Ariz. ed. 3: 23 1969.
Full publication details for this name can be found in IPNI: urn:lsid:ipni.org:names:87440-2.