Variation
var. arizonicus
This Cactus produce are fused stems up to 230 mm (9in) tall by 255 mm (10 in) thick with 10 ribs and a dark grey radial spines up to 38 mm (1½ in) long with pinkish-tan central spines. It produces a scarlet flower to 50 mm (2in) wide during summer.

var. gurneyi

var. gonacanthus
This cactus produces dull greenish cylindrical stems up to 60 mm (2⅜ in) thick with 7-9 acute ribs.  Areoles have 8-thick greyish radial spines up to 20 mm (¾ in) long and a single central yellowish black-tipped spine is up to 60 mm (2⅜ in) long. The diurnal vivid yellowish orange cup-shaped flower is up to 50 mm (2 in) long and appears during summer.

var. intermis

var. melanacanthus
This clump forming cactus has many stems up to 150 mm (6 in) long by 50 mm (2 in) thick with 9-10 tuberculate ribs. The areoles have 5-11greyish radial spines and 1-3 central spines up to 60 mm (2⅜ in) long. The bright red funnelform diurnal flowers are up to 60 mm (2⅜ in) long by 40 mm (1⅝ in) wide appearing during mid summer.

var. mojavensis
This small cactus forms dense spreading clumps with pale greyish green stems up to 200 mm (7¾ in) tall by 50 mm (2 in) thick. The whitish areoles are spaced 10 mm (⅜ in) apart and have 10 radial spines that are reddish then turning grey to 25 mm (1 in) long and 1-central spine to 50 mm (2 in) long. The come on red funnel shaped diurnal flowers are up to 50 mm (2 in) long and wide and appear during mid summer.

var. neomexicanus
This clump forming cactus has 5-45 upright stems to 300 mm (1 ft) tall by 100 mm (4in) thick with 8-12 ribs.  The areoles have 9-12 radial spines up to 38 mm (1½ in) long and 2-4 central spines that are tan or pink ageing to grey. The come on red flowers are up to 38 mm (1½ in) wide and appear during summer from Texas to Arizona and northern Mexico.

var. paucispinus