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 12303883) with original publication details: Rhododendrons Magnolias Camellias 1974: 47 1974.
This name was in version 1 of The Plant List, record tro-12303883, and has not been changed.