This name is a synonym of Dactylorhiza majalis subsp. occidentalis (Pugsley) P.D.Sell.
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 100362239) with original publication details: Proc. Linn. Soc. Lond. 148: 124 1936.
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 Orchis majalis in version 1 of The Plant List.