The identification of Engelmann's tuberculosa with Scheer's strobiliformis was made by Dr. Engelmann himself upon an examination of Scheer's type. The use of the specific name tuberculosa is necessitated by the law of homonyms, as strobiliformis had been used twice already before it was taken up by Scheer. M. strobiliformis Muhlenpf. is C. scolymoides sulcatus; and M. strobiliformis Engelm. is C. conoideus. 57. Cactus viviparus Nutt. in Fraser's Cat. (1813). Mamillaria vivipara Haw. Syn. Succ. Suppl. 72 (1819). Low and depressed-globose, usually proliferous and cespitose (forming large masses), but sometimes simple: tubercles terete and loose, lightly grooved: radial spines 12 to 20, stiff and white, often dark-tipped, 6 to 8 mm. long; central spines usually 4 (sometimes less, often more, even as many as 8), brownish, 8 to 12 mm. long, 3 spreading upwards, the lowest stouter and shorter and deflexed: flowers about 3.5 cm. long (large for the size of the plant) and even broader when expanded, bright purple: stigmas pointed with a short mucro: fruit oval, pale green, juicy, 12 to 18 mm. long: seeds yellowish-brown, obliquely obovate and curved about the small hilum, 1.4 to 1.6 mm. long). (Ill. Cact. Mex. Bound. t. 74. fig. 3, seeds) Type unknown. On the northwestern plains, from the boundary provinces of British America (western Manitoba, Assiniboia and Alberta), and throughout the Upper Missouri region, southward through western Nebraska to western Kansas and to the eastern foothills of central Colorado. It is also mentioned by Howell (Cat. of Oregon, Washington and Idaho plants), as occurring beyond the Rocky Mountain divide in Idaho and Washington, which is probable, but no specimens have been seen. Specimens examined: Montana (Hayden, nos. 1854, 1855; Vernon Bailey of 1890, near Bridger): Colorado (Hayden of 1869): Nebraska (Rydberg 1379 of 1893, Thomas Co.): also specimens cultivated in St. Louis in 1869; also growing in Mo. Bot. Gard. 1893. It seems best to keep this northwestern form specifically separate from that large assemblage of southern forms that have been commonly referred to it. The forms referred to this species from western Kansas (Smyth's check list) have not been examined, and they may represent intermediate forms, inclining to simple habit and ovate form, as in the Colorado forms. The southern type (C. radiosus) is distinguished from C. viviparus not only by its very different range, but also by its ovate to cylindrical form, simple habit, more numerous (12 to 40) and longer (6 to 22 mm.) radial spines, usually more numerous (3 to 14) central spines in which the upper are more robust than the lower, porrect lower central, obtuse stigmas, and brown obovate straight seeds. 58. Cactus radiosus (Engelm.). Mamillaria vivipara Engelm. Pl. Fendl. 49 (1849), not Haw. (1819). Mamillaria radiosa Engelm. Pl. Lindh. 196 (1850). Mamillaria vivipara radiosa texana Engelm. Syn. Cact. 269 (1856).