This name is a synonym of Carex atrata subsp. aterrima (Hoppe) Hartm..
The record derives from WCSP
(data supplied on 2012-03-23)
which reports it as a synonym (record 342720) with original publication details: J. Fac. Sci. Univ. Tokyo, Sect. 3, Bot. 8(4): 198 1962.
This name was in version 1 of The Plant List, record kew-342720.