Echinocactus williamsii Lem. Allg. Gart. Zeit. xiii. 385
(1845).
Anhalonium williamsii Lem. in Forst Handb. Cact. i. 233
(1846).
Hemispherical, from a very thick root, often densely proliferous,
transversely lined below by the remains of withered tubercles:
ribs usually 8 (in young specimens often 6), very broad,
gradually merging above into the distinct nascent tubercles which
are crowned with somewhat delicate penicellate tufts, which
become rather inconspicuous pulvilli on the ribs: flowers small,
whitish to rose: stigmas 4. (Ill. Bot. Mag. t. 4296) Type
unknown.
Along the Lower Rio Grande, Texas, and extending southward into
San Luis Potosi and southern Mexico.