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 12303875) with original publication details: Rhododendron Camellia Year Book 17: 164 1963.
This name was in version 1 of The Plant List, record tro-12303875, and has not been changed.