Origin and Habitat: Bolivia ( and also Brazil & Paraguay) South America.
Habitat: G. damsii (anisitsii) grows in open areas under the protection of low bushes. It often form large groups and is extremely variable.

• Gymnocalycium damsii var. rotundulum Backeb.

• Gymnocalycium anisitsii (K.Schum.) Britton & Rose
• Echinocactus anisitsii K.Schum.
• Gymnocalycium anisitsii subs. damsii (K.Schum.) G.J.Charles
• Echinocactus damsii K.Schum.
• Gymnocalycium damsii Britton & Rose
• Gymnocalycium anisitsii subs. damsii f. cristatum hort.
• Gymnocalycium damsii f. cristatum hort.
• Gymnocalycium anisitsii subs. damsii f. monstruosum hort.
• Gymnocalycium damsii f. monstruosum hort.
• Gymnocalycium anisitsii subs. damsii f. variegata hort.
• Gymnocalycium damsii f. variegata hort.
• Gymnocalycium anisitsii var. griseopallidum H.Till & Amerh.
• Gymnocalycium griseo-pallidum Backeb.
• Gymnocalycium anisitsii var. tucavocense Backeb. ex H.Till & Amerh.
• Gymnocalycium damsii var. tucavocense Backeb.
• Gymnocalycium damsii var. boosii Amerh.
• Gymnocalycium damsii var. centrispinum Backeb.
• Gymnocalycium damsii subs. evae Halda, Horáček & Milt
• Gymnocalycium damsii var. rotundulum Backeb.
• Gymnocalycium joossensianum Britton & Rose
• Echinocactus joossensianus Boed.

• Gymnocalycium anisitsii subs. multiproliferum (P.J.Braun) P.J.Braun & Esteves
• Gymnocalycium damsii var. multiproliferum P.J.Braun

• Gymnocalycium anisitsii var. tucavocense cv. Red Form
• Gymnocalycium damsii var. tucavocense cv. Red Form

Description: Gymnocalycium damsiiSN|13315]]SN|13319]] var. rotundulum (Gymnocalycium anisitsiiSN|13319]]SN|13315]]) is a usually solitary colourful cactus common in cultivation, characterized by rounder and scarcely raised tubercles. However it is very similar (if not identical) to the standard G. damsii (G. anisistsii) and it is probably the exact same plant.
Stem: Up to 10 cm tall, 8-10 cm in diameter colourful and highly decorative, with characteristic horizontal clear and dark strips. The clear areas (above the areoles) are pastel-grey-pink while the dark zone (below the areoles) are deep olive-green to brown-purple.
Spines: Nearly useless in terms of defence.
Remarks: Seems to be a pretty variable plant you might get some other names which are effectively the same plant.... and also not sure all plants identified as this are really this.

Bibliography: Major references and further lectures
1) Edward Anderson “The Cactus family” Timber Press, Incorporated, 2001
2) 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
3) David R Hunt; Nigel P Taylor; Graham Charles; International Cactaceae Systematics Group. "The New Cactus Lexicon" dh books, 2006
4) N. L. Britton, J. N. Rose “The Cactaceae. Descriptions and Illustrations of Plants of the Cactus Family.” Volume 4, The Carnegie Institution of Washington, Washington 1923
5) Curt Backeberg “Die Cactaceae: Handbuch der Kakteenkunde” Gustav Fischer Verlag, Stuttgart New York 1982–1985
6) E. W Putnam “GYMNOCALYCIUMS: A Guide for Growers” National Cactus & Succulent Society. Handbook No. 5. 1978

Cultivation and Propagation: It is a summer grower species that offers no cultivation difficulties. Water regularly in summer (but do not overwater ) Keep this plant almost dry in winter at a minimum temperature of 0°C, prefer relatively rich substrate and low pH compost (if possible not limestone) otherwise growth will stop altogether. Feed with a high potassium fertilizer in summer. It is quite frost resistant if kept dry (hardy to -5° C)
Sun Exposure: Light shade. It may tolerate bright situations but is likely to suffer from sun scorch or stunted growth if over exposed to direct sunlight during the hottest part of the day in summer. This plant needs plenty of space for its roots, repotting should be done every other year or when the it has outgrown its pot. This species is particularly easy and accommodating, seldom suffer of cryptogamic diseases.
Propagation: Direct sow after last frost. (seldom produces offsets)