Opuntia polyacantha var. nicholii
Cact. Succ. J. (Los Angeles) 70: 188. 1998.
Stem segments narrowly to broadly obovate, 10–27 × 7–18 cm; areoles 8–11 per diagonal row across midstem segment, 12–30 mm apart. Spines in most areoles, of 2 kinds: major spines 1–5 per areole, down curved, ascending near stem segment apex, pink-gray or basal 2/3 brown to black, the longest 45–150 mm; minor spines 3–8 per areole, deflexed, white to gray, 60–220 cm (spine clusters easily detached in preparing specimens). Fruits stout; areoles 18–24, most bearing 3–12 spines, 8–17 mm. 2n = 66.
Phenology: Flowering spring.
Habitat: Barren areas with saltbush and ephedra, limestone or red, sandy soils
Elevation: 1200-1300 m
"longest" is not a number.