This name is a synonym of Vigna vexillata (L.) A.Rich..
The record derives from ILDIS
(data supplied on 2010-07-14)
which reports it as a synonym (record
This name record (from ILDIS) 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 Phaseolus vexillatus in version 1 of The Plant List.