Origin and Habitat: Guanajuato, Durango, San Luis Potosi, and Queretaro, Mexico.

• Mammillaria gigantea Hildm. ex K.Schum.
• Neomammillaria gigantea (Hildm. ex K.Schum.) Britton & Rose

• Mammillaria gigantea Hildm. ex K.Schum.
• Neomammillaria gigantea (Hildm. ex K.Schum.) Britton & Rose
• Mammillaria armatissima R.T.Craig
• Mammillaria gigantea var. flavovirens Rogoz. & Plein
• Mammillaria gigantea subs. hamiltonhoytiae (Bravo) Rogoz. & Plein
• Mammillaria hamiltonhoytiae (Bravo) Werderm. in Backeb.
• Neomammillaria hamiltonhoytiae Bravo
• Mammillaria hamiltonhoytiae var. fulvaflora R.T.Craig
• Mammillaria hastifera Krainz & A.C.Keller
• Mammillaria ocotillensis R.T.Craig
• Mammillaria ocotillensis var. brevispina R.T.Craig
• Mammillaria ocotillensis var. longispina R.T.Craig
• Mammillaria saint-pieana Backeb.

Description: Solitary or clumping
Stems: Depressed globose with apex strongly sunken and woolly, up to 10 cm tall, 17 cm in diameter,.
Tubercles: Pyramidal, four-angled, with latex, axils woolly.
Central spines: 4-6, robust, straight or more or less curved,dark yellow, becoming brownish
with age, to 20 mm long, lowermost one longest.
Radial spines: 7-12, needle-like, white, to 3 mm long.
Flowers: Yellowish green, to 15 mm in diameter.
Fruits: Pink to greenish.
Seeds: Brown.