This name is a synonym of Vicia pulchella Kunth.
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 13035052) with original publication details: Nomencl. Bot. (ed. 2) 2(12–13): 765 1841.
This name record (from Tropicos) 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 Vicia subulata in version 1 of The Plant List.