This name is a synonym of Antennaria alpina (L.) Gaertn..
The record derives from TICA
(data supplied on 2012-02-11)
which reports it as a synonym (record BE9BD9F3-3F0D-4D8A-BB98-639529A1630E).
This name record (from TICA) 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 Antennaria porsildii in version 1 of The Plant List.