Mammillaria pachycylindrica Backeb. Mammillaria pachycylindrica Backeb. in Cact. Succ. J. Gr. Brit. 21: 82. 1959 sec. Guzmán & al. 2003=Mammillaria mexicensis R.T. Craig, Mammillaria Handb.: 311. 1945 syn. sec. Guzmán & al. 2003