The Neolloydia conoidea complex (N. conoidea, N. grandiflora, N. ceratites, N. texensis, and N. matehualensis) is shown to consist of a single species, N. conoidea. Neolloydia conoidea is compared with Echinomastus spp. and with N. warnockii; the latter is more closely related to Echinomastus and should be included in that genus. Several members of the Cactinae are compared on the basis of 26 characters. These data show that Gymnocactus, Turbinicarpus, Rapicactus, and Normanbokea should be included in Neolloydia to create a larger, newly-defined genus containing the following 15 species: N. conoidea, N. subterranea, N. mandragora (comb. nov.), N. valdeziana (comb. nov.), N. pseudopectinata (comb. nov.), N. gielsdorfiana, N. viereckii, N. horripila, N. smithii (=G. beguinii), N. saueri, N. knuthiana, N. schmiedickeana (comb. nov.), N. lophophoroides (comb, nov.), N. pseudomacrochele (comb. nov.), and N. laui (comb. nov.). Thelocactus is a closely related but separate genus.