This name is a synonym of Rumex bucephalophorus subsp. canariensis (Steinh.) Rech.f..
The record derives from WCSP (in review)
(data supplied on 2012-03-23)
which reports it as a synonym with original publication details: Bot. Jahrb. Syst. 33: 413 1904.
This name was in version 1 of The Plant List, record kew-2869599, and has not been changed.