Obregonia denegrii
(Photo: Wen-Chung Fan)
fans@igc.org
http://go2.163.com/cactusfan

This is the white "crown" as we call it here. I got it when I visited a C&S buddy in the nearby city of Tianjin.
http://go2.163.com/cactusfan/cactus112700/Obregoniadenegriivariegate.jpg