Origin and Habitat: Coahuila, Mexico.
Habitat: This plant is a mud crack dweller, growing almost sunken in cracks in the dry lake at the Laguna de Viesca. Altitude 1.000 to 1.230 m

• Mammillaria conzattii (Britton & Rose) Orcutt
• Mammillaria confusa var. conzattii (Britton & Rose) R.T.Craig
• Neomammillaria conzattii Britton & Rose

• Mammillaria karwinskiana Mart.
• Cactus karwinskianus (Mart.) Kuntze
• Neomammillaria karwinskiana (Mart.) Britton & Rose
• Mammillaria confusa (Britton & Rose) Orcutt
• Mammillaria pyrrhocephala var. confusa (Britton & Rose) Borg
• Neomammillaria confusa Britton & Rose
• Mammillaria confusa var. centrispina R.T.Craig
• Neomammillaria confusa var. centrispina (R.T.Craig) Y.Itô
• Mammillaria confusa var. robustispina R.T.Craig
• Mammillaria conzattii (Britton & Rose) Orcutt
• Mammillaria confusa var. conzattii (Britton & Rose) R.T.Craig
• Neomammillaria conzattii Britton & Rose
• Mammillaria ebenacantha Shurly
• Mammillaria fischeri Pfeiff.
• Cactus fischeri (Pfeiff.) Kuntze
• Mammillaria jozef-bergeri Wojnowski & Prajer
• Mammillaria karwinskiana var. virens (Scheidw.) Salm-Dyck
• Cactus virens (Scheidw.) Kuntze
• Mammillaria virens Scheidw.
• Mammillaria multiseta Ehrenb.
• Mammillaria nagliana Repp.
• Mammillaria neomystax Backeb.
• Neomammillaria neomystax (Backeb.) Y.Itô
• Mammillaria neomystax var. rhodacantha Y.Itô
• Neomammillaria neomystax var. rhodacantha (Y.Itô) Y.Itô
• Mammillaria praelii Muehlenpf.
• Cactus praelii (Muehlenpf.) Kuntze
• Mammillaria viridis var. praelii (Muehlenpf.) Salm-Dyck
• Neomammillaria praelii (Muehlenpf.) Britton & Rose
• Mammillaria strobilina Tiegel
• Mammillaria tropica Repp.

• Mammillaria karwinskiana subs. beiselii (Diers) D.R.Hunt
• Mammillaria beiselii Diers

• Mammillaria karwinskiana subs. collinsii (Britton & Rose) D.R.Hunt
• Mammillaria collinsii (Britton & Rose) Orcutt
• Mammillaria voburnensis subs. collinsii (Britton & Rose) U.Guzmán
• Mammillaria voburnensis var. collinsii (Britton & Rose) Repp.
• Neomammillaria collinsii Britton & Rose
• Mammillaria voburnensis var. quetzalcoatl Repp.

• Mammillaria karwinskiana subs. nejapensis (R.T.Craig & E.Y.Dawson) D.R.Hunt
• Mammillaria nejapensis R.T.Craig & E.Y.Dawson
• Mammillaria nejapensis f. aureispina (Y.Itô)
• Neomammillaria nejapensis var. aureispina Y.Itô
• Mammillaria nejapensis f. brevispina (R.T.Craig & E.Y.Dawson) Krainz
• Mammillaria nejapensis var. brevispina R.T.Craig & E.Y.Dawson
• Neomammillaria nejapensis var. brevispina (R.T.Craig & E.Y.Dawson) Y.Itô
• Mammillaria nejapensis f. elegans (Y.Itô)
• Neomammillaria nejapensis var. elegans Y.Itô
• Mammillaria nejapensis f. longispina (R.T.Craig & E.Y.Dawson) Krainz
• Mammillaria nejapensis var. longispina R.T.Craig & E.Y.Dawson
• Neomammillaria nejapensis var. longispina (R.T.Craig & E.Y.Dawson) Y.Itô
• Mammillaria nejapensis var. typica R.T.Craig & E.Y.Dawson

Description: Small geophyte cactus, with a heavy tap root that may exceed the size of the plant above soil level. Stems solitary flattened globose, blue-green, up to 5 cm high and alsoin diameter.
Spines: About 12-16, thin, bristle-like radial spines, slightly pubescent with darker tips, up to 6 mm long. Central spine: not present or 1, straight, needle-like, darker, up to 6 mm long.
Flowers: White with pinkish midveins, very early in the season, February/March.
Fruits: Red clavate.

Cultivation and Propagation: This species has few special demands. Whatever view one adopts, it is worth a place in every Mammillaria collection. The only problem is that it is very slow growing, a plant for patient growers.
Like all thick-rooted species, it requires careful watering (rot sensitive), and patience to match its slow growth. During the winter rest, the plant may pull near the surface of the potting mix.
Propagation: Direct sow after last frost. (it usually doesn't produces offsets).