This name is a synonym of Rhododendron augustinii subsp. chasmanthum (Diels) Cullen.
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 12303882) with original publication details: Quart. J. Amer. Rhodod. Soc. 30: 210 1976.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:332016-1.
This name was in version 1 of The Plant List, record tro-12303882, and has not been changed.