Globose or subconical, 3.5 to 6.5 cm. in diameter, simple:
tubercles terete, conical, grooved above, 10 to 12 mm. long:
radial spines 16 to 30, pectinate, straight or little curved,
rigid and appressed (interwoven with neighboring clusters),
ashy-white (often dusky at apex), 8 to 12 mm. long, the uppermost
longer (12 to 20 mm.); central spines 3 or 4, the upper ones
turned upward and intermixed with the radials, the lower one very
stout, 15 mm. long, subulate from a very thick bulbous base,
straight (rarely slightly curved) and porrect (deciduous in old
specimens): flowers 3 to 5 cm. long: fruit oval, elongated, about
2 cm. long, green: seeds elongated-obovate. brown and smooth,
about 1.8 mm. long. (Ill. Cact. Mex. Bound. t. 10) Type, the
Wright and Bigelow specimens in Herb. Mo. Bot. Gard.

On limestone hills, from the Pecos River, southwestern Texas, and
southern New Mexico, westward to the Rio Grande (from Presidio
del Norte northward). Fl. June.

Specimens examined: Texas (Wright of 1849, 1851, 1852; Bigelow of
1852; Engelmann, with no number or date; Evans of 1891).

The characteristic appearance of the plant is given by the very
stout and straight central spine standing in each cluster
perpendicular to the plant body. The range of this species,
between the Pecos and the upper Rio Grande, suggests another
separated group, such as is presented by C. scolymoides sulcatus
to the east, between the Brazos and Nueces. Very frequently
specimens of C. echinus occur in which some of the tubercles do
not develop central spines, and then the spine characters
resemble those of C. radians. In C. radians, also, an occasional