++ Central spines 3 to 12.
54. Cactus conoideus (DC.) Kuntze, Rev. Gen. Pl. 260 (1891).
Mamillaria conoidea DC. Rev. Cact. 112 (1829).
Mamillaria strobiliformis Engelm. Wisliz. Rep. 113 (1848), not
Scheer (1850).
Ovate-conical, 3.5 to 10 cm. high, 4 to 7 cm. in diameter below, with densely woolly vertex, simple: tubercles conical, about 12 mm, long, closely appressed-imbricate ("giving the plant the appearance of a pineapple or cone"): radial spines 10 to 16, ashy to white, straight and stout, 6 to 10 mm. long, the upper longer (10 to 15 mm.); central spines 3 to 5, stouter, brownish-black, 10 to 16 mm. long, the two or three smaller ones erect-spreading, the single lower one more rigid, porrect or deflexed, 15 to 20 mm. long: flowers 2 to 3 cm long and wide, deep purple: fruit unknown. (Ill. DC. Mem. Cact. t. 2) Type unknown.
On rocks, Coahuila and Nuevo Leon to San Luis Potosi and southern
Mexico.
Specimens examined: Coahuila (Palmer 378 of 1882; Pringle 3117 of 1890): Nuevo Leon (Wislizenus of 1847): San Luis Potosi (Poselger of 1851; Eschanzier of 1891).
55. Cactus potsii (Scheer) Kuntze, Rev. Gen. Pl. 261 (1891).
Mamillaria potsii Scheer in Salm Cact. Hort. Dyck. 104 (1850).
Cylindrical, 30 to 35 cm. high, 2.5 to 3 cm. in diameter, somewhat branching: tubercles ovate, obtuse, very lightly sulcate, with somewhat woolly axils: radial spines very numerous (entirely covering the whole plant), slender and white; central spines 6 to 12, stouter from a broad base: flowers large, green, or reddish: fruit red. Type unknown.
From the Rio Grande region, near Laredo, Texas, to Chihuahua.