Mamillaria sulphurea Forst. Handb. Cact. (1846), not Cactus
sulphureus Gill, (1830).
Mamillaria rhodantha sulphurea Salm, Hurt. Cact. Dyck. 11
(1850).
Central spines sulphur-yellow; otherwise like the species. Type
unknown.
San Luis Potosi.
Specimens examined: San Luis Potosi (Pfeiffer, with no number or
date; Eschanzier of 1891).
The varietal distinction maintained seems a small one, but it is
constant and striking, so far as can be discovered.