This name is a synonym of Penstemon laricifolius subsp. exilifolius (A. Nelson) D.D. Keck.
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 50110081) with original publication details: Univ. Wyoming Publ. Sci., Bot. 1(4): 97 1924.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:187591-2.
This name was in version 1 of The Plant List, record tro-50110081.