This name is a synonym of Thuja plicata Donn ex D.Don.
The record derives from WCSP
(data supplied on 2012-03-23)
which reports it as a synonym (record 465085) with original publication details: Bibl. Cult. Trees 47 1949.
This name record (from WCSP) was not included in version 1 of The Plant List. It is possible the same name was included from a different data source, to check this you can search for Thuja plicata in version 1 of The Plant List.