Depressed-globose, 2 to 3 cm. high: tubercles 8 mm. long, with long axillary wool: radial spines 25 to 30, white and capillary, 10 to 25 mm. long; central spines 2 to 4, slender and naked (or slightly puberulent), the most central one hooked (usually upwards), 15 to 25 mm. long, the upper 1 to 3 shorter and straight, all yellow with red tips, the hooked one often brownish-red nearly to the base: flowers unknown: fruit green, about 4 mm. long: seeds cinnamon-brown, oblique, broadly obovate, with narrowly ovate basal hilum. Type unknown. San Luis Potosi, so far as known. Poselger says, "Texas, auf der Seira de Bocas, among rocks," which station we have been unable to locate. Specimens examined: San Luis Potosi (Eschanzier of 1891): also specimens cultivated in Hort. Pfersdorff in 1869; in Mo. Bot. Gard. in 1891; also growing in Mo. Bot. Gard. 1893. The capillary radials give the plant a white-woolly appearance. The younger spines at the vertex are erect and tufted. It resembles C. grahami, but the tubercles are much more slender and not thickened at base, all the spines are more slender, the central hooked one is more reddish, and the fruit is much shorter. 21. Cactus eschanzieri, sp. nov. Depressed-globose, 3 cm. in diameter, simple: tubercles broader at base, 6 to 8 mm. long, with naked axils: spines all pubescent; radials 15 to 20, with dusky tips, the lateral 10 to 12 mm. long, the lower weaker, shorter and curved, the upper shorter; solitary central spine reddish, slender, somewhat twisted, usually hooked upwards, 15 to 25 mm. long: flowers red (?): fruit reddish (?), ovate, about 10 mm, long: seeds reddish, oblique-obovate, 1.2 mm. long, pitted, with subventral hilum. Type in Herb. Coulter. San Luis Potosi. Specimens examined: San Luis Potosi (Eschanzier of 1891). Resembles C. grahami, but with fewer and more slender pubescent spines, longer and less rigid central, more exserted fruit, and much larger reddish and strongly pitted seeds with subventral hilum. 22. Cactus tetrancistrus (Engelm.). Mamillaria tetrancistra Engelm. Am. Jour. Sci. II. xiv. 337 (1852), in part. Mamillaria phellosperma Engelm. Syn. Cact. 262 (1856). Cactus pellospermus Kuntze, Rev. Gen. Pl. 261 (1891).