Opuntia mesacantha Rafinesque var. vaseyi J. M. Coulter, Contr. U. S. Natl. Herb. 3: 431. 1896; O. humifusa Rafinesque var. vaseyi (J. M. Coulter) A. Heller; O. littoralis (Engelmann) Cockerell var. austrocalifornica L. D. Benson & Walkington; O. littoralis var. vaseyi (J. M. Coulter) L. D. Benson & Walkington; O. rafinesquei Engelmann var. vaseyi (J. M. Coulter) K. Schumann

Shrubs, sprawling to spreading, to 1.2 m. Stem segments not disarticulating, green, flattened, obovate to elliptic, 7-22 × 5-12 cm, ± tuberculate, glabrous, glaucous; areoles 5-7(-8) per diagonal row across midstem segment, subcircular to elliptic, 3-6 × 2.5-3.5 mm; wool gray. Spines absent or 1-6 per areole, over distal 0-70% of stem segment, spreading to reflexed, yellow with chalky white coat and brown to yellow basal portions, aging dark red, straight, subulate, angularly flattened, the longest 20-48 mm. Glochids moderately dense in crescent at adaxial edge of areole and sparse or poorly developed in subapical tuft, yellow, aging red-brown, of unequal lengths, to 4 mm. Flowers: inner tepals yellow, orange, or dull red throughout, 25-35 mm; filaments orange-yellow sometimes darker near base; anthers yellow; style pink to red (rarely white); stigma lobes green to yellow-green. Fruits red-purple throughout, obovoid to subcylindric, 30-55 × 20-40 mm, juicy, glabrous, spineless; areoles 20-36. Seeds tan to gray, 4.5-6 mm diam.; girdle protruding to 0.5 mm. 2n = 66.

Flowering spring (Apr-May). Coastal sage scrub, chaparral, grassy hillsides, disturbed sites; 30-600 m; Calif.

The nothospecies Opuntia ×vaseyi resulted from hybridization between O. littoralis and O. phaeacantha (B. D. Parfitt and M. A. Baker 1993).