This name is a synonym of Anthoceros laevis f. aquatica (Walt. Watson) Macvicar.
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 35204292) with original publication details: Proc. Somersetshire Archaeol. Nat. Hist. Soc. 66: 157 1921.
This name was in version 1 of The Plant List, record tro-35204292.