Rebutia (Aylostera) simoniana was first described by Walter Rausch in Kakteen und andere Sukkulenten 35(9): p.p. 204-5, the journal of the Deutsche Kakteen-Gesellschaft, in 1984.The description is reproduced here in the original Latin, and a note in German, together with my own translations in English. You should look up the original for more details, including a colour photograph.

Simplex, globosa, ad 25 mm diametiens, clare-viridis, radicibus aequis; costis 13 paulum spiraliter tortis, in tubercula 2-3 mm longa divisis; areolis rotundis ad ovalibus, 1-1,5 mm longis, albo- ad clare-fusco- tomentosis; aculeis marginalibus 11-13, ad 5 mm longis, fragilibus, vitreo-albis; aculeis centralibus 1 -4, ad 7 mm longis, validioribus, fusco-acuminatis.

Floribus 35 mm longis et diametientibus, ovario et receptaculo clare-ochraceo, squamis obscurioribus, pilis et setis albis tecto; phyllis perigonii exterioribus rotundis, tenui-acuminatis, clare-ochraceis, medio-viridi-violaceo-striatis; phyllis perigonii interioribus rotundis, pure aurantiacis; fauce 17 mm longa,
dimidio cum stylo connata, alba; filamentis, stylo, stigmatibus (4) albis. Fructu globoso, 6 mm diametiente, olivaceo, pilis et setis albis tecto. Seminibus maioribus quam Aylosterae fiebrigii Guerke, globoso-galeiformibus, 1,2 mm longis, brunneis, hilo lato, recto.

Patria: Bolivia, Cinti australis supra La Cueva, 3500 m alt.

Typus: Rausch 739, depositus in Collectione Plantarum Succulentarum Municipali Turicensi, Helvetia.

Additional notes

Als ich vor einigen Jahren wiederholt durch Bolivien reiste und zum dritten Male den kleinen Ort La Cueva (nahe Culpina) besuchte, sammelte ich routinemäßig einige Exemplare von Rebutia fiebrigii (Guerke) Britton & Rose. Diese Rebutia hat ein relativ großes Verbreitungsgebiet, man findet sie nahe Santa Viktoria (Argentinien) über Iscayachi (Typstandort) bis Camargo und auch in La Cueva. Wie die Rebutia fiebrigii aussieht, zeigt uns WERDERMANN in seinem Buch „Blühende Kakteen”, Tafel 118, mit dem Hinweis, daß die Pflanze seiner Abbildung vermutlich noch aus der Zeit GUERRES stammt.
Wie groß war aber mein Erstaunen, als in der Kultur zwischen den Rebutia fiebrigii aus La Cueva, viel später als zur Blütezeit derselben, große orange Blüten erschienen! Erst jetzt bemerkte ich das uniforme Aussehen von 6 kleineren Stücken, die ich immer für nicht ausgewachsene Rebutia fiebrigii gehalten habe. Der Habitus zeigt Ähnlichkeit mit Rebutia buiningiana Rausch, unterscheidet sich aber von dieser durch kleineren Wuchs, anderen Farbton in der Blüte und größeren Samen.
Ich verehre dieses Kleinod meinem langjährigen Freund und Rebutienliebhaber Wilhelm SIMON.

English translation

Solitary, spherical up to 25 mm in diameter, light green with even roots; 13 ribs, somewhat spiralling, divided into 2-3 mm tubercles; areoles round to oval, 1-1.5 mm long, with white to light brown wool; 11-13 radial spines, up to 5 mm long, brittle, glassy white; 1-4 central spines, up to 7 mm long, stronger and with a brown tip.

Flower 35 mm long and in diameter, ovary and tube light ochre with darker scales, white hairs and bristles; outer petals round with a fine tip, light ochre with a green-violet central stripe; inner petals round, pure orange; throat 17 mm long, half fused with the style, white; filaments, styles and stigmas (4) white.

Fruit spherical, 6 mm in diameter, olive-coloured with white hairs and bristles. Seeds larger than Rebutia fiebrigii (Guerke) Britton & Rose, helmet-shaped, 1.2mm, dark brown with broad straight umbilicus.

Habitat: above La Cueva, Sud Cinti, Bolivia at an altitude of 3500 m.

Type Rausch 739, deposited in the Zurich Municipal Succulent Collection.

A few years ago, when I repeatedly traveled through Bolivia and visited the small town of La Cueva (near Culpina) for the third time, I routinely collected a few specimens of Rebutia fiebrigii (Guerke) Britton & Rose. This Rebutia has a relatively large distribution area, it can be found near Santa Viktoria (Argentina) through Iscayachi (type location) to Camargo and also in La Cueva. WERDERMANN shows us what Rebutia fiebrigii looks like in his book “Blühende Kakteen”, Plate 118, with the note that the plant in his illustration probably dates back to the GUERRES period. But how amazed I was when large orange flowers appeared in cultivation, flowering much later than the Rebutia fiebrigii from La Cueva! Only now did I notice the uniform appearance of 6 smaller plants, which I always thought were immature Rebutia fiebrigii. The habit shows similarity to Rebutia buiningiana Rausch, but differs from it by smaller growth, different color of the flower and larger seeds. I honor this gem to my friend of many years and lover of the Rebutias Wilhelm SIMON.