Subspecies, varieties, forms and cultivars of plants belonging to the Mammillaria grahamii/sheldonii group

• Mammillaria alamensis R.T.Craig: (Mammillaria grahamii subs. sheldonii) without or with only 1 central spine, about 9 radial spines, white, tipped brown, needle-like, about 6 to 8 mm long. Distribution: Sierra de Alamos, Alamos, Sonora, Mexico.
• Mammillaria grahamii Engelm.: has 20-35 white to greyish to light brown to reddish radial spines. 1-4 central spines yellowish to dark brown central, one usually hooked. It is very variable. Distribution: California, Arizona, New Mexico and Texas, USA; Sonora, Sinaloa and Chihuahua, Mexico.
• Mammillaria grahamii subs. sheldonii (Britton & Rose) D.R.Hunt: has 9-24 radial spines. Central spines either straight or hooked, 1-1,5 cm long. Flowers purplish-pink with a pinkish brown midstripe. It is variable. Distribution: Mexico (Sonora and Chihuahua).
• Mammillaria gueldemanniana Backeb.: aside from bigger flowers, not many differences. Distribution: Mexico, Chihuahua, Sonora and Sinaloa.
• Mammillaria gueldemanniana var. guirocobensis (R.T.Craig) Backeb.: (Mammillaria grahamii subs. sheldonii) has 1-3 reddish-brown central spines almost 1 cm long. One spine is hooked. Flowers bigger and widely open. Distribution: Sonora, Sinaloa, Chihuahua at higher altitudes.
• Mammillaria inaiae R.T.Craig: (Mammillaria grahamii subs. sheldonii)
• Mammillaria marnieriana Backeb.: (Mammillaria grahamii subs. sheldonii)
• Mammillaria microcarpa Engelm. in Emory: (Mammillaria grahamii) has 15-35 pale radial spines and 1-3, yellowish-brown to purplish black centrals, the longest hooked. Fruits scarlet. Distribution: USA (Texas, New Mexico, Utah, California and Arizona) and Mexico.
• Mammillaria microcarpa var. auricarpa W.T.Marshall: (Mammillaria grahamii) has pale, radial spines and a yellowish brown hooked central spine. Flowers are 4 cm in diameter, pink, and are followed by golden yellow berries. Distribution: U.S.A. (Arizona).
• Mammillaria microcarpa f. cristata hort.: crested form.
• Mammillaria oliviae Orcutt: (Mammillaria grahamii)
• Mammillaria pseudoalamensis Backeb.: (Mammillaria grahamii subs. sheldonii) variant recognisable from M. alamensis for the absence of central spines, and larger flowers with a characteristic distinctive orange pistil. Distribution: West of Alamos, Sonora, Mexico.
• Mammillaria swinglei (Britton & Rose) Boed.: (Mammillaria grahamii subs. sheldonii) has wide funnelform purplish pink flowers up to 3. Stile style pink, twice as long as the pink filaments; stigma-lobes 8, linear, pointed, green.