This name is a synonym of Euphorbia capitellata Engelm..
The record derives from WCSP
(data supplied on 2012-03-23)
which reports it as a synonym (record 38222) with original publication details: Publ. Field Mus. Nat. Hist., Bot. Ser. 2: 411 1916.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:55422-2.
This name was in version 1 of The Plant List, record kew-38222, and has not been changed.