This name is a synonym of Vigna vexillata var. dolichonema (Harms) Verdc..
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 13040472) with original publication details: Notizbl. Bot. Gart. Berlin-Dahlem 14: 113 1938.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:525342-1.
This name was in version 1 of The Plant List, record tro-13040472, and has not been changed.