This name is a synonym of Amaranthus powellii S.Watson.
The record derives from WCSP (in review)
(data supplied on 2012-03-23)
which reports it as a synonym with original publication details: Vierteljahrsschr. Naturf. Ges. Zürich 52: 443 1908.
This name was in version 1 of The Plant List, record kew-2632779, and has not been changed.