This name is a synonym of Mimulus tenellus var. procerus (A.L. Grant) Hand.-Mazz..
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 50056792) with original publication details: Ann. Missouri Bot. Gard. 11: 207, pl. 3, f. 2 1924.
This name was in version 1 of The Plant List, record tro-50056792, and has not been changed.