Mammillaria barbata or really cochemeia barbata and formerly mammillaria viridiflora from Mt Lemmon, AZ. These plants have done well for us when grown in a semi-shaded location under an oak or Rhus. They are zone 6 plants. They need more protection and care than mammillaria wrightii. But these little plants are so interesting they are worth trialing in your garden in a warmer microclimate. Green to cream flowers all summer long with precipitation.