This name is a synonym of Adiantum madagascariense var. prolongatum (Bonap.) Tardieu.
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 26603279) with original publication details: Notes Pteridol. 4: 79 1917.
This name was in version 1 of The Plant List, record tro-26603279.