This name is a synonym of Pycnanthemum flexuosum (Walter) Britton, Sterns & Poggenb..
The record derives from WCSP
(data supplied on 2012-03-23)
which reports it as a synonym (record 135080) with original publication details: Sp. Pl. 571 1753.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:452818-1.
This name was in version 1 of The Plant List, record kew-135080.