Echinocactus horizonthalonius Lem.
A small turbiniform cactus of low, rocky slopes found in southeastern Arizona & southern New Mexico. Seems particularly fond of limestone.
Plant habit near the northeast base of Bennett Mountain, San Andres Mountains, Doña Ana County, New Mexico, 9 Feb 2010.
Plant habit on Tortugas Mountain on the east side of Las Cruces, Doña Ana County, New Mexico, 24 Sep 2004.