A robust globose or ovate simple form (7.5 to 10 cm. in diameter), with long (12 to 25 mm.) deeply-grooved tubercles, 15 to 20 long (10 to 30 mm.) rigid whitish radial spines, and 3 to 6 centrals deep brown above. Type, the specimens of Cous, Palmer, Bischoff and Johnson, all in Herb. Mo. Bot. Gard. Sandy and rocky soil from southern Utah through northern and western Arizona to southern California. Specimens examined: Arizona (Cous of 1865; Cous & Palmer of 1865 and 1872; Palmer of 1869; Bischoff of 1871; Miller of 1881; Rusby 617 of 1853; Pringle of 1884): Utah (Johnson of 1871, 1872, 1874; Parry of 1875, 1877): California (Parish of 1880): also specimens cultivated in Mo. Bot. Gard. in 1881; and in Meehan's Gard. in 1882. 61. Cactus radiosus deserti (Engelm.). Mamillaria deserti Engelm. Bot. Calif. ii. 449 (1880). Subglobose or oval (5 to 10 cm. high) and simple, with deeply grooved tubercles (slender and about 12 mm. long), 25 to 30 rather long (10 to 16 mm.) grayish white radial spines (the larger with reddish tips), 3 or 4 shorter and stouter centrals with 5 or 6 intermediate ones above, small (2.5 cm. long) straw-colored flowers (becoming purplish-tipped), 5 or 6 stigmas, and obliquely obovate curved seeds. Type, Parish 433 in Herb. Mo. Bot. Gard. In the mountains bordering the deserts of southeastern California (San Bernardino County) and extending to central Nevada (Reese River Valley). Specimens examined: California (Parish 453 of 1880, also of 1882; Bailey of 1890): Nevada, Lincoln County (Coville & Funston of 1891, Death Valley Expedition): also specimens cultivated in Meehan's Gard. in 1882. The smaller straw-colored flowers alone suggest the propriety of keeping this form specifically distinct, but even in size and color there is an occasional tendency toward the specific character. The obliquely obovate curved seeds resemble those of C. viviparus. The plant densely covered with stout ashy-gray interlocking spines is easily recognized. 62. Cactus radiosus chloranthus (Engelm.). Mamillaria chlorantha Engelm. Wheeler's Rep. 127 (1878). Oval to cylindrical (7.5 cm. in diameter, sometimes 20 to 22.5 cm. high), with 20 to 25 gray radial spines almost in two series, 6 to 9 stouter reddish or brownish-tipped centrals (12 to 25 mm. long), and yellowish or greenish-yellow flowers 3.5 cm. long and wide. Type: Southern Utah specimens of both Parry and Johnson occur in Herb. Mo. Bot. Gard., but they are all referred to C. radiosus arizonicus, and I can find no trace of any specimens of C. radiosus chloranthus in the Engelmann collection. Southern Utah, east of St. George (Parry; Johnson). The plant is evidently near C. radiosus deserti, of which variety it seems to be the Utah representative, but in the absence not only of the type, but even of authentic specimens, the two are kept separate, a thing fully justified by the description. 63. Cactus radiosus alversoni, var. nov.