Description:Coryphantha scheeriSN|10314]]SN|10315]] v. validais the New Mexican form of the widespreadCoryphantha robustispina subs. scheeriSN|10314]]SN|10314]](=Mammillaria scheeriSN|10325]]SN|10325]]Mühlenpfordt 1845). The var.validawas firstly described asMammillaria scheeriSN|10325]]SN|10325]] var. validaby Engelmann in 1856 without having seenMammillaria scheeriSN|10325]]SN|10325]]Mühlenpfordt. Engelmann had presumed that his var.validamight be just a somewhat larger and more heavily spined northern form ofMammillaria scheeriSN|10325]]SN|10325]](from Chihuahua in northern Mexico). When visiting the collection of Prince Salm-Dyck, he found original plants ofMammillaria scheeriSN|10325]]SN|10325]]which corresponded completely with his var.valida, thus confirming his initial assumption. As Engelmann himself had realised already, var.validadoes not contain enough distinct criteria to delineate a variety or subspecies and it should be fully synonymized withMammillaria scheeriSN|10325]]SN|10325]](Coryphantha robustispina subs. scheeriSN|10315]]SN|10314]]).
Subspecies, varieties, forms and cultivars of plants belonging to the Coryphantha robustispina group
Coryphantha robustispina(A.Schott ex Engelm.) Britton & Rose: (Subsp.robustispina) is typically larger and has a single curved or hooked central spine. Distribution: Arizona.
Coryphantha robustispina subs. scheeri(Muehlenpf.) N.P.Taylor: has straight central spines. Distribution: USA (west Texas, New Mexico) and Mexico (Chihuahua)
Coryphantha robustispina subs. uncinata(L.D.Benson) N.P.Taylor: has strongly curved or hooked central spines. Distribution (Arizona, New Mexico, west Texas) and Mexico (Chihuahua).
Coryphantha scheeri var. valida(Engelm.) L.D.Benson in L.D.Benson: this is the New Mexican form ofCoryphantha robustispina subs. scheeri. It is not enough distinct to delineate a variety or subspecies.
