This name is a synonym of Opuntia macrorhiza subsp. pottsii (Salm-Dyck) U. Guzmán & Mandujano.
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 5108169) with original publication details: Contr. U.S. Natl. Herb. 13(9): 310 1911.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:174984-2.
This name was in version 1 of The Plant List, record tro-5108169, and has not been changed.