Globose, 3.5 to 7.5 cm. in diameter, simple: tubercles conical,
from a 4-angled base, lower ones short (4 to 6 mm.), upper
flower-bearing ones longer (10 to 12 mm.), terete and grooved:
radial spines 16 to 24, somewhat recurved from a bulbous
compressed base, stiff and pectinate, horny or whitish (at length
ashy), interwoven with adjacent clusters, those on lower
tubercles about equal (6 to 10 mm.), on flower-bearing tubercles
elongated, mixed with a few stouter ones and fasciculated (lower
ones 10 to 12 mm. long, upper ones 12 to 18 mm. long and forming
an apical tuft); centrals none: flowers over 5 cm. long and about
6 to 7.5 cm. in diameter when expanded, bright sulphur-yellow:
fruit ovate and green, about 12 mm. long: seeds compressed,
brownish smooth and shining, 1.8 mm. long. (Ill. Cact. Mex.
Bound. t. 11) Type unknown; that of M. pectinata Engelm. is the
Wright material in Herb. Mo. Bot. Gard.

Extending from the hills along the Lower Pecos to El Paso,
southwestern Texas, southward through Coahuila and San Luis
Potosi to southern Mexico.

Specimens examined: Texas (Wright 226 of 1849, also of 1852;
Evans of 1891): Coahuila (Palmer of 1880; Mrs. Nickels): San Luis
Potosi (Parry & Palmer 265; Eschanzier of 1891): also specimens
cultivated in St. Louis in 1853; in Mo. Bot. Gard. in 1892; and
in Harv. Bot Gard.

Even in the absence of the type I have ventured to refer
Mamillaria pectinata Engelm. to this species. Dr. Engelmann had
concluded that the two were "not sufficiently distinct," and the
examination of Mexican forms which pass as C. radians abundantly