Mamillaria compacta Engelm. Wisliz. Rep. 21 (1848).
Depressed-globose, 5 to 10 cm. in diameter, simple: tubercles
short-conical, crowded, 8 mm. long: radial spines 13 to 16,
rigid, recurved and appressed, interwoven with adjacent clusters,
whitish or horny, 10 to 20 mm. long; the erect central spine
often wanting: flowers 3 to 3.5 cm. long and broad, yellow
(brownish without): fruit oval, green: seeds 1.4 mm. long, smooth
and yellow. (Ill. Cact. Mex. Bound. t. 74. fig. 2, seeds) Type,
Wislizenus of 1846 in Herb. Mo. Bot. Gard.
Mountains of Chihuahua. Fl. June-July.
Specimens examined: Chihuahua (Wislizenus of 1846): also
specimens cultivated in St. Louis in 1848, 1850, 1854.