S. lunata, Dammann, and vars. umbrosa and minuta (Rüst in Monatsschr. Kakt. vi. 43) are either hybrid forms or slight variations of S. variegata, var. marmorata, differing only as follows:— S. lunata, corolla-lobes minutely ciliate, very dark purple-brown or blackish-purple with a pale yellow crescent-shaped marking and 2–3 specks near the apex of each lobe and a pair of yellowish marks at each sinus; annulus rather lighter than the lobes, speckled with yellow. Var. umbrosa, corolla-lobes not ciliate, somewhat reticulated with whitish-yellow at the tips only; annulus with larger whitish markings; outer corona-lobes with dots at the apical part only, no central stripe. Var. minuta, corolla-lobes minutely ciliate, with a pale yellowish marking something like a flattened ring with 2 teeth on each; annulus with a few small yellowish marks; outer corona-lobes with the teeth slightly diverging. S. marmorata, Rüst, l.c. 38, is totally different from S. marmorata, Jacq., and merely a hybrid form of S. variegata with a corolla 2 3/4 in. in diam., minutely ciliate on the lobes, which are margined and marked with a few large spots and blotches of dark purple-brown; annulus paler with a few smaller purple-brown spots.