Typically solitary, body globular to 12 cm wide. Tubercles prominent, 4-sided. Axils white woolly. 2-6 white central spines, tips dark and hooked 6 mm long, 22-24 whitish radial spines 8 mm long. Flowers white to pale pink, 1 cm wide. Fruit reddish purple. [M. ritteriana Boed.]
Source: (1997). Cactaceae. In: . Horticultural Flora of South-eastern Australia. Volume 2. Flowering plants. Dicotyledons. Part 1. The identification of garden and cultivated plants. University of New South Wales Press.