This name is a synonym of Nepeta grandiflora M.Bieb..
The record derives from WCSP
(data supplied on 2012-03-23)
which reports it as a synonym (record 460185) with original publication details: Linnaea 21: 674 1849.
This name record (from WCSP) was not included in version 1 of The Plant List. It is possible the same name was included from a different data source, to check this you can search for Nepeta mussinii in version 1 of The Plant List.