Mammillaria ritteriana
Hunt refers this species to M.chionocephala; it is a distinctive variant with finer and longer spination
Mammillaria ritteriana Z 40
Z 40 - Ramos Arizpe - Coahuila - Mexico
Referred to Mammillaria chionocephala
Mammillaria ritteriana Z 40
Z 40 - Ramos Arizpe - Coahuila - Mexico
Referred to Mammillaria chionocephala
Mammillaria ritteriana SB 265
SB 265 - Ramon Arispe - Coahuila - Mexico
Referred to Mammillaria chionocephala
Mammillaria ritteriana ROG 192
ROG 192 - Huigueras - Nuevo Leon - Mexico
from UK Mammillaria reference collection
Referred to Mammillaria chionocephala