Etymology -The name is a combination of Mammillaria and Neolloydia which are similar.
It should be no surprise that the single species in Mammilloydia had long been included in Mammillaria. After all, the factor separating it is primarily, if not soley, the characteristics of the seeds. Mammilloydia seeds feature a smooth surface with no perisperm. The stems are globose with tubercles, white spines, and bristles in the axils. Areoles are dimorphic and tubercles have no groove - traits typical of Mammillaria. Also similar, the flowers are funnel-shaped, cream-colored with a dark pink or brownish mid-stripe. Flowers come from second-year growth axils and later give rise to berry-like red-pink fruits.
Mammilloydia is primarily a Chihuahuan species from North-Central Mexico and it is popular among collectors. It is prized for its tidy appearance and of course the ability to easily collect all (1) species within the genus!