This name is a synonym of Arabis hirsuta var. pycnocarpa (M.Hopkins) Rollins.
The record derives from WCSP (in review)
(data supplied on 2012-03-23)
which reports it as a synonym with original publication details: Rhodora 39: 117 1937.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:17207-2.
This name was in version 1 of The Plant List, record kew-2646108.