21. Opuntia littoralis (Engelmann) Cockerell, Bull. S. Calif. Acad. Sci. 4: 15. 1905.
Opuntia engelmannii Salm-Dyck var. littoralis Engelmann in W. H. Brewer et al., Bot. Calif. 1: 248. 1876; O. lindheimeri Engelmann var. littoralis (Engelmann) J. M. Coulter; O. occidentalis Engelmann var. littoralis (Engelmann) Parish; O. semispinosa Griffiths
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).