Bull. Torrey Bot. Club 43: 523. 1916.
Shrubs, low, forming mats, 10–30 cm. Stem segments easily detached to firmly attached, green, flattened, narrowly to broadly obovate, 3.5–9 × 2.5–5 cm, low tuberculate, glabrous; areoles 4–6(–7) per diagonal row across midstem segment, oval, 3.5 × 2.5 mm; wool white. Spines in most areoles, straight, acicular, terete; major spines 0–1 per areole, reflexed to porrect (rarely ascending), gray-white to brown, (15–)25–40(–60) mm; intermediate spines 0–3, reflexed, 12–20 mm; minor spines 2–4, reflexed, yellow-gray, 3–6 mm. Glochids loosely packed, in small tuft or crescent at adaxial margin of areole, yellowish, inconspicuous, to 4 mm. Flowers: inner tepals yellow throughout, 30–45 mm; filaments white to red; anthers yellow; style white; stigma lobes green. Fruits rarely set, top-shaped to barrel-shaped, 15–20 × 15 mm, glabrous; areoles 10–15, most bearing 3–12 spines or distal spines bearing 1–3 spines. Seeds tan, large, 5–7 mm; girdle protruding 1–1.5 mm. 2n = 66.
Phenology: Flowering summer (late Jun-early Jul).
Habitat: Dark basaltic cliffs and derived sands
Elevation: 100-800 m
B.C., Idaho, Oreg., Wash.