[Opuntia covillei var. piercei (Fosberg) Munz, moreOpuntia engelmannii var. littoralis Engelm., Opuntia occidentalis var. littoralis (Engelm.) Parish, Opuntia occidentalis var. piercei (Fosberg) Munz, Opuntia phaeacantha var. piercei Fosberg]
Shrubs, spreading to sprawling, forming large clumps, to 1 × 1-9 m. Stem segments not disarticulating, green, flattened, elliptic to obovate to rhombic, 15-25(-40) × 6.5-14 cm, ± tuberculate, glabrous, usually glaucous; areoles 5-7(-8) per diagonal row across midstem segment, prominent, subcircular(-oval), 4-6 × 4-5 mm, enlarging in age; wool gray. Spines 4-11 per areole, in most areoles, yellow with chalky white coat, to yellow with red-brown basal portions, aging reddish gray; erect ones terete, stout, straight; abaxial ones reflexed, shorter, to 12 mm; adaxial spines spreading, longest spines 20-40 mm. Glochids moderately dense in crescent at adaxial edge of areole, merging with subapical tuft when present, yellow to red-brown, to 5 mm. Flowers: inner tepals yellow to dull red throughout, 35-45 mm; filaments yellow to orange-yellow; anthers yellow; style pink to red; stigma lobes yellow-green to green. Fruits dark red-purple throughout, obovoid, 35-50 × 30-35 mm, juicy, glabrous, spineless; areoles 22-36. Seeds gray, subcircular, warped, 3-4.5 mm diam.; girdle protruding 0.5 mm. 2n = 66. Flowering spring (Apr-May). Coastal sage scrub, chaparral; 10-400 m; Calif. (including Channel Islands); Mexico (Baja California).