This name is a synonym of Begonia riedelii A.DC..
The record derives from WCSP
(data supplied on 2012-03-23)
which reports it as a synonym (record 460337) with original publication details: Rodriguésia 18: 26 1945.
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 Begonia riedelii in version 1 of The Plant List.