Mamillaria/Coryphantha: Note that Budd's Flora places this species in genus Mamillaria, while Flora of Alberta places it in genus Coryphantha.  The following are the answers to the key questions in these flora that lead to Mamillaria or Coryphantha. 

	globose or cushion-like plants; NOT [plants branched and jointed, the stems more or less flattened]
	flowers red or purple; NOT [flowers yellow or orange]

Cactaceae: Answers to key questions in Budd's Flora  leading to this family. 

	succulent, spiny plants with leaves absent or scale-like, inconspicuous; NOT [plants with leaves]
	flowers with two floral rings, and with each petal distinct from the others