This name is a synonym of Ziziphus taylorii (Britton) M.C. Johnst..
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 50305647) with original publication details: Bull. New York Bot. Gard. 3: 445 1905.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:227796-2.
This name was in version 1 of The Plant List, record tro-50305647, and has not been changed.