Specimens collected by Mrs. Anna B Nickels across the Rio Grande from Laredo, Texas, and showing neither flower nor fruit, seem to intergrade between C. scolymoides and C. scolymoides sulcatus. The habit is that of the former, the tubercles are those of the latter, while the spines are somewhat different from either. The number of central spines in these specimens is very hard to determine, as on the adult tubercle they all assume a radial position. The usual adult arrangement is an apparent absence of central spines; 10 to 12 rigid, spreading and more or less recurved radials (increasing in length from the lowest), which are mostly white or the upper more or less dusky; and above, just behind the radial row, 2 or 3 stout recurved-ascending spines, which are white with tips more or less reddish-black, one of the spines usually much stouter and longer than the others. This form may represent a distinct species, but it seems very unsafe to add species to the C. scolymoides group without the fullest information. Prince Salm-Dyck refers C. scolymoides to "M. daimonoceras Lem. Cact. gen. nov., p. 5," but no mention of such a name can be found in the work referred to. Labouret refers C. corniferus to the same name and reference. If "M. daimonoceras" was anything more than a garden or herbarium name used by Lemaire I have been unable to find it, and Dr. Engelmann's notes indicate that his search met with the same result. It is possible that the name was applied loosely to this assemblage of closely related forms that seem to cluster about C. corniferus. A most perplexing question of relationship is presented by the forms that have been called pectinatus, scolymoides, sulcatus (calcaratus), Echinus, and the Mexican forms radians, impexicomus, corniferus. It may be that they are all merely varieties of one strong polymorphic type, but our knowledge of corniferus is so incomplete, and material of other forms is so scanty, that I can not venture to make such an assertion. However, it seems probable that radians, pectinatus, scolymoides, sulcatus and Echinus all have green fruit, while in impexicomus and corniferus it is red. It has also seemed proper to merge radians and pectinatus, also impexicomus and corniferus, and to refer sulcatus to scolymoides as a variety. These seven forms are thus reduced at least to four species. 49. Cactus scolymoides sulcatus (Engelm.). Mamillaria sulcata Engelm. Pl. Lindh. 246 (1845), not Pfeiff. (1848). Mamillaria strobiliformis Muhlenpf. Allg. Gart. Zeit. xvi. 19 (1848), not Scheer (1850). Mamillaria calcarata Engelm. Pl. Lindh. 195 (1850). Cactus calcaratus Kuntze, Rev. Gen. Pl. 259 (1891).