This name is a synonym of Penstemon newberryi subsp. sonomensis (Greene) D.D. Keck.
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 50080462) with original publication details: Pittonia 2(10C): 218 1891.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:187777-2.
This name was in version 1 of The Plant List, record tro-50080462.