This name is a synonym of Ranunculus occidentalis var. nelsonii (DC.) L.D. Benson.
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 50324012) with original publication details: Proc. Amer. Acad. Arts 8: 374 1872.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:1210630-2.
This name was in version 1 of The Plant List, record tro-50324012, and has not been changed.