Plants usually unbranched (branched with age, forming large clumps to 80 cm diam. at low elevation in Brewster County, Texas), usually relatively smooth except for protruding abaxial central spine, stem largely obscured by spines. Roots diffuse or short taproots. Stems spheric (ovoid or conic with age) to cylindric, 3-15(-20) × 3-7.6 cm; tubercles 8-12 × 6-11 mm, firm; areolar glands seasonally conspicuous; parenchyma not mucilaginous; pith 1/4-1/3 of lesser stem diam.; medullary vascular system absent. Spines 16-34 per areole, drab whitish, pale yellowish tan, or pale purplish gray, overlying relatively bright yellow to dark yellow-brown inner layers, later gray with dark tips; radial spines 15-25(-29) per areole, 16-24 × 0.2-0.6 mm; subcentral spines (0-)2-3(-4) per areole, erect; central spines (0-)1-4(-11) per areole, larger spines and abaxial central spine porrect, straight or slightly curved downward (rarely strongly recurved), others appressed, abaxial (or only) central spine 11.5-25 × 0.3-0.9 mm, rigid, others slightly longer and thinner. Flowers nearly apical, 25-65 × 25-65 mm; outer tepals entire; inner tepals 20-37 per flower, bright yellow, sometimes proximally reddish, 22-34 × 4.5-12 mm; outer filaments reddish, reddish orange, or yellow; anthers bright yellow-orange; stigma lobes 10-13, whitish or greenish yellow, 3-4 mm. Fruits green, ovoid, 12-28 × 10-19 mm, slimy; floral remnant strongly persistent . Seeds reddish brown, somewhat comma-shaped, 1.7-1.9 mm, smooth, shiny. 2n = 22 (as C. cornifera var. echinus).
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