This name is a synonym of Sagittaria latifolia Willd..
The record derives from WCSP
(data supplied on 2012-03-23)
which reports it as a synonym (record 451877) with original publication details: Rep. (Annual) Missouri Bot. Gard. 6: 16 1894.
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 Sagittaria variabilis in version 1 of The Plant List.