<i>Mammillaria heyderi var. heyderi</i>; native to S.W. United States, N. Mexico.  Photographed at the Desert Botanical Garden, Phoenix, AZ.
<a href="//commons.wikimedia.org/wiki/User:Davepape" title="User:Davepape">Dave Pape</a>
CC BY 2.5
<span class="int-own-work" lang="en">Own work</span>