Origin and Habitat: Uruguay (Tacuarembó)

• Notocactus mueller-melchersii var. eugeniae (Vliet) N.Gerloff & Neduchal
• Notocactus eugeniae Vliet
• Parodia mammulosa subs. eugeniae (Vliet) Hofacker
• Ritterocactus mammulosus subs. eugeniae (Vliet) Doweld

• Parodia mueller-melchersii (Backeb.) N.P.Taylor
• Notocactus mueller-melchersii Frič ex Backeb.
• Notocactus mueller-moelleri Frič ex Backeb. & F.M.Knuth
• Ritterocactus mueller-melchersii (Frič ex Backeb.) Doweld
• Notocactus mueller-melchersii var. eugeniae (Vliet) N.Gerloff & Neduchal
• Notocactus eugeniae Vliet
• Parodia mammulosa subs. eugeniae (Vliet) Hofacker
• Ritterocactus mammulosus subs. eugeniae (Vliet) Doweld
• Notocactus rutilans f. robustior N.Gerloff
• Notocactus rutilans var. robustior N.Gerloff
• Notocactus rutilans var. roseiflorus (H.Schloss. & Bredero) N.Gerloff & Neduchal
• Notocactus roseiflorus H.Schloss. & Bredero
• Parodia rutilans (Däniker & Krainz) N.P.Taylor
• Notocactus rutilans Däniker & Krainz
• Ritterocactus rutilans (Däniker & Krainz) Doweld
• Parodia rutilans subs. veeniana (Vliet) Hofacker
• Notocactus mueller-melchersii var. veenianus (Vliet) N.Gerloff & Neduchal
• Notocactus veenianus Vliet
• Ritterocactus rutilans subs. veenianus (Vliet) Doweld

• Parodia mueller-melchersii subs. gutierrezii (W.R.Abraham) Hofacker
• Notocactus gutierrezii W.R.Abraham
• Notocactus rutilans var. gutierrezii (W.R.Abraham) N.Gerloff & Neduchal
• Ritterocactus mueller-melchersii subs. gutierrezii (W.R.Abraham) Doweld

• Parodia mueller-melchersii subs. winkleri (Vliet) Hofacker
• Notocactus mueller-melchersii var. winkleri (Vliet) N.Gerloff & Neduchal
• Notocactus winkleri Vliet
• Ritterocactus mueller-melchersii subs. winkleri (Frič ex Backeb.) Doweld

Description: Globose cactus, up to 7 cm in diameter.
Spines: Red an white
Flowers: Blossoms are large (6 cm in diameter) and stand near the top. They are yellow with glossy petals and have a dark purple stigma. The buds are tomentose and appear during the summer.
Remarks: Notocactus eugeniaeSN|17645]]SN|17645]] is generally included within (as a synonym of) Parodia mammulosaSN|17641]]SN|20022]] but quite dissimilar at a first glance. This plant is now more properly considered by synonym of Parodia mueller-melchersiiSN|20022]]SN|17641]] (Backeb.) N.P. Taylor.

Bibliography: Major references and further lectures
1) Edward F. Anderson “The Cactus Family” Timber Press, 2001
2) Curt Backeberg “Cactus Lexicon” Sterling Publishing Company, Incorporated, 1978
3) Hiroshi Hirao “Colour encyclopaedia of cacti” Japan 1979 (Japanese language and script)
4) Willy Cullmann, Erich Götz (Dozent Dr.), Gerhard Gröner “The encyclopedia of cacti” Portland, OR: Timber Press, 1986
5) David Hunt, Nigel Taylor “The New Cactus Lexicon” DH Books, 2006 ISBN 0953813444, 9780953813445
6) James Cullen, Sabina G. Knees, H. Suzanne Cubey “The European Garden Flora Flowering Plants: A Manual for the Identification of Plants Cultivated in Europe, Both Out-of-Doors and Under Glass” Cambridge University Press, 11/Aug./2011

Cultivation and Propagation: It is easy to grow. It prefers a neutral to slightly acidic mineral-based potting mix with plenty of extra grit and feed during the summer. It likes a warm bright location, does great in partial shade but doesn't like full, hot blazing sun in the central summer month. Can support quite some water during the growing season but pot plants in winter are wet-sensitive and needs to be kept dry (rots easily if soil is wet and cold) tends to lose its roots in winter. Water Best if watered with rain water. Usually it is recommended to over-winter this plant in a bright and warm greenhouse with at least 8-10° C and rather dry (it tends to lose its roots and to rot if the substrate is wet and cold) but it has proved to tolerate temperatures as low as -5° C for short periods.
Propagation: Seeds.