This name is a synonym of Dactylorhiza majalis subsp. occidentalis (Pugsley) P.D.Sell.
The record derives from WCSP
(data supplied on 2012-03-23)
which reports it as a synonym (record 142972) with original publication details: Bot. Soc. Exch. Club Brit. Isles 11: 458 1937 publ. 1938.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:648928-1.
This name was in version 1 of The Plant List, record kew-142972.