Globose, 7.5 cm. in diameter, simple: tubercles short, with woolly axils: radial spines about 25, erect-spreading, slender but rigid, yellow (brownish to black with age), unequal, 8 to 10 mm. long; central spines 6, a little longer (10 to 12 mm.) and straight, more rigid and darker, black-tipped: seeds obovate, reddish-brown, 1 mm. long. Type in Herb. Coulter. Very easily distinguished by its dense, erect spines, which so completely cover the plant as to give it the appearance of a large chestnut bur. Another much smaller form, which seems to be a variety, has stouter and longer ashy-white spines, the centrals darker-tipped, and the lower centrals slightly curved. ++ One short central spine (rarely two or none): ovaries immersed: seeds small, yellow and rugulose: simple. 5.Cactus heyderi (Muhlenpf.) Kuntze, Rev. Gen. Pl. 260 (1891). Mamillaria heyderi Muhlenpf. Allg. Gart. Zeit. xvi. 20(1848). Mamillaria declivis Dietr. Allg. Gart. Zeit. xviii. 235 (1850). Mamillaria applanata Engelm. Pl. Lindh 198 (1850). Mamillaria texensis Labouret, Monogr. Cact. 89 (1858). Depressed, globose, usually with depressed vertex, 8 to 12 cm. broad, 2.5 to 5 cm. high: tubercles elongated: radial spines 10 to 22, whitish, 5 to 12 mm. long, the lower usually the longer, stouter, and often darker; central spine 4 to 8 mm. long, light yellowish-brown, stout, straight, and porrect: flowers 2 to 2.5 cm. long, reddish-white: fruit incurved, 1.5 to 3 cm. long. (Ill. Cact. Mex. Bound. t. 9. figs. 4-14). Type unknown. From the Guadalupe River, Texas, to the mouth of the Rio Grande, and westward to Arizona and Sonora. Fl. April, May. Specimens examined: Texas (Lindheimer of 1845, 1847, 1853; Wright 226, also collections of 1849, 1852, 1853, 1855, 1856; Bigelow of 1853; Trelease of 1892; Nealley of 1892): New Mexico (Wright 311; Bigelow of 1853, Evans of 1891): Arizona (Pringle of 1881): also growing in Mo. Bot. Gard. 1893; and in the World's Fair collection of Mrs. Nickels. The radial spines are somewhat variable in relative length, often becoming almost equal, while sometimes the upper radials are very much reduced. The figure referred to in Cact. Mex. Bound. is not satisfactory as to the general habit of the plant, which is flat-topped rather than hemispherical. 6.Cactus heyderi hemisphaericus (Engelm.). Mamillaria hemisphaerica Engelm. Pl. Lindh. 198 (1850). Differs in being hemispherical instead of flat-topped, in its fewer (9 to 12) and shorter (4 to 8 mm.) radial spines, and much smaller less rough and lighter-colored seeds. (Ill. Cact. Mex. Bound. t. 9. figs. 15-17) Type, the "Goebel's Garden" plants in Herb. Mo. Bot. Gard. Throughout southern Texas and southern New Mexico, and southward; not extending so far north or west as the species, and apparently not so abundant within the United States. Fl. May.