The Mazca Brush Bush, known regionally as Escobilla or Escobilla de Masca, reached a height of about 1 m, it is, or rather was a broom-like semi-parasitic shrub with very small scale-like, stiff and pointed leaves.
The species is now considered extinct, as the last two specimens were found in 1983. The main reasons for its extinction are found in the uncontrolled grazing by introduced goats and rabbits.
The other three species of the genus, the Gran Canaria Brush Bush (Kunkeliella canariensis Stearn) from the island of Gran Canaria as well as the Rue Brush Bush (Kunkeliella retamoides Santos) and the Fleshy Brush Bush (Kunkeliella subsucculenta Kämmer), both from Tenerife, are also extremely threatened.
 Peter und Ingrid Schönfelder: Die Kosmos Kanarenflora. Franckh-Kosmos-Verlag Stuttgart 1997  Thomas Abeli; Giulia Albani Rocchetti; Zoltan Barina; Ioannis Bazos; David Draper; Patrick Grillas; José María Iriondo; Emilio Laguna; Juan Carlos Moreno-Saiz; Fabrizio Bartolucci: Seventeen ‘extinct’ plant species back to conservation attention in Europe. Nature Plants 7: 282-286. 2021
This species was described in 1857, it is/was endemic to the island of Gran Canaria, Canary Islands.
The shell reaches/reached a size of about 2 cm in diameter.
The Guanarteme Land Snail appears to have been quite common formerly.:
“The present Helix was taken in Gran Canary both by Grasset and Fritsch, and subsequently in considerable abundance by Mr. Lowe and myself. We found it principally in and around the little town of Teror (on one occasion even within the house of Don Pedro Manrique), but likewise in the region of El Monte, – particularly in the hollows of old trees at the Laurealos, ….” 
The species is listed (as Hemicycla guamartemes) in the Red List of the IUCN as ‘data deficient’, but, since it apparently was not found during recent searches, may be already extinct.
 T. Vernon Wollaston: Testacea Atlantica: or the Land and Freshwater Shells of the Azores, Madeiras, Salvages, Canaries, Cape Verdes, and Saint Helena. London: L. Reeve & Co. 1878