Autor: Britton & Rose

“Flower on the nipple”, because in this genus, flowers are situated at the top of the tubercles of the species.
A genus of tiny plants, solitary to densely branched, variable in shape, size, spination, and colour. Stem more or less flattened, clavate, covered by dense tiny spines. Central and radial spines usually indiscernible.
Flowers diurnal, very small, appearing at the apex of stems, bell-shaped, white to pale pink, pollinated by small insects, although a species (E. micromeris) is self-fertile. Fruits clavate to elongated, naked, indehiscent, red, containing few seeds. Seeds helmet-shaped, shiny, papillose or reticulate, black.
The genus Epithelantha usually grows on limestone or basalt soils, in gravel or crevices of rocks, in a matorral (xerophytic scrub), with many cacti and other succulents, in the middle of a vegetation of spiny shrubs, or in the shade in forests, but also in full sun, in desert grasslands of the Chihuahuan desert, among bushes, from 300 m (E. ilariae) up to 2300 m in altitude (E. pachyrhiza). Some natural sowings develop including in the selaginellas (spikemosses) which sometimes accompany them (Selaginella lepidophylla, pers. obs.).
Mexico (Chihuahua, Coahuila, Durango, Nuevo Leon, San Luis Potosi), USA (Arizona, New Mexico, Texas).

Currently 7 possible species + 6 likely subspecies:
– Epithelantha bokei* L.D.Benson 1969
– Epithelantha cryptica D.Donati & Zanovello 2011
– Epithelantha greggii (Engelm.) Orcutt 1926
– Epithelantha greggii subsp. polycephala (Backeberg) D.Donati & Zanovello (2010)
– Epithelantha greggii subsp. potosina D.Donati & Zanovello 2010
– Epithelantha ilariae D.Donati & Zanovello 2010
– Epithelantha micromeris* (Engelm.) F.A.C.Weber 1898
– Epithelantha pachyrhiza Backeb. 1954
– Epithelantha pachyrhiza subsp. elongata (Backeberg) D.Donati & Zanovello (2010)
– Epithelantha pachyrhiza subsp. parvula D.Donati & Zanovello 2010
– Epithelantha pachyrhiza subsp. pulchra D.Donati & Zanovello 2010
– Epithelantha unguispina (Boed.) D.Donati & Zanovello 2010
– Epithelantha unguispina subsp. huastecana D.Donati & Zanovello 2010

References: "TAXONOMY of the CACTACEAE" -  ISBN 978-84-617-3723-9 (Vol. 1)