This name is a synonym of Vigna luteola var. angustifolia (Engelm. & A. Gray) S. Watson.
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 13012849) with original publication details: Boston J. Nat. Hist. 5: 214 1845.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:265144-2.
This name was in version 1 of The Plant List, record tro-13012849, and has not been changed.