This name is a synonym of Cirsium pumilum var. hillii (Canby) B. Boivin.
The record derives from TICA
(data supplied on 2012-02-11)
which reports it as a synonym (record 487D6FDF-2DF7-45F4-A13E-D8B390CEF6FB) with original publication details: Rhodora 10 95 1908.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:59033-2.
This name was in version 1 of The Plant List, record gcc-127865.