By a misprint in Cact. Mex. Bound, the specific name appeared as "Goodridgii," and this error appears in almost every subsequent mention of the species, even in Watson's Bibliographical Index, although in Syn. Cact. and other references by Dr. Engelmann the correct form appears. 17. Cactus pondii (Greene). Mamillaria pondii Greene, Pittonia, i, 268 (1889). Oval or cylindrical, from low to 30 cm. high, simple or sparingly branched: radial spines 20 to 30, white and slender; centrals 4 or 5, the longest over 25 mm, long, rigid and strongly hooked, dark brown above the middle: flowers nearly 5 cm. long, bright, scarlet: fruit unknown. Type, Pond specimens in Herb. Greene. Cedros Island, off the west coast of Lower California. Fl. February. Unfortunately, the type specimen has been mislaid, so that no examination of it could be made. Evidently related to C. goodrichii, but differing in its much more robust habit, more numerous radials, much longer spines, and larger scarlet flowers. 18. Cactus barbatus (Engelm.) Kuntze, Rev. Gen. Pl. 261 (1891). Mamillaria barbata Engelm. Wisliz. Rep. 22 (1848). Depressed-globose, about 4 cm. in diameter, simple: tubercles 8 mm. long, with naked axils: radial spines very numerous (50 to 60), in two series, 6 to 8 mm. long, the outer (about 40) slender but rigid and white, the inner (10 to 15) a little stouter and yellow; usually one central spine, stout and erect, hooked downwards, brownish: flowers 18 to 20 mm. long, rose-red: fruit oblong, 10 to 12 mm. long, green (when mature?): seeds minute, dark brown and lightly pitted. (Ill. Cact. Mex. Bound t. 6. figs. 9-12) Type, Wislizenus of 1846 in Herb. Mo. Bot. Gard. Central Chihuahua. Fl. May, in cultivation. Specimens examined: Chihuahua (Wislizenus of 1846, 1850): also specimens cultivated in Baumann's Garden in 1857, 1858; also growing in Mo. Bot. Gard. 1893. Dr. Engelmann observed a curious intermediate character in the origin of the flowers of this species, the first ones of the season appearing in the axils of the last tubercles of the preceding year, while the later ones develop from the axils of the first tubercles of the same season. The specimen growing in Mo. Bot. Gard, in 1893 had 3 central spines, one or two being hooked. 19. Cactus grahami (Engelm.) Kuntze, Rev. Gen. Pl. 260 (1891). Mamillaria grahami Engelm. Syn. Cact. 262 (1856).