A 
y 
brevi-ovatis axilla lanata setigeris ; aculeis radiantibus 11-15 albidis, 
centralibus 3-4 fusco-atris, inferiore paulo longiore deorsum unci- 
nato; floribus lateralibus. 
San Diego, California. — Two or three inches high. Radial 
spines 2|-3| lines long; the lower central spine a little longer. 
Flowers apparently yellowish-white, and half an inch in diameter. 
§ 3. Setose Salm. 
9. M. bicolor, Lehm.: depressa, ovata, s. cylindracea, prolifera ; 
axilhs lanatis ; tuberculis parvulis conicis ; aculeis exterioribus 16-20 
tenuissimis recurvato-radiantibus, centralibus 2-4rigidis, majoribus ' 
albis apiee nigris interdum subpollicaribus, supremo plerumque longis- 
simo incurvo ; floribus parvulis purpureis; stigmatibus 5. 
Abundant on the calcareous hills of the Rio Grande below Laredo, 
Texas, Dr. Poselger: fl. June and July. — Plant 3 - 12 inches high, 
the larger specimens 2-3 inches in diameter; radial spines 1-2, 
lower central ones 4-5, the upper 6 - 10 lines long. Flower about 
9 lines long. 
§ 4. Centrispina , Salm. (All our species are simple and 
have a milky juice.) 
10. M. Heyderi, Muhlenpf. (1848): simplex, depresso-globosa; 
tuberculis elongatis pyramidatis subquadrangulatis; aculeis radianti¬ 
bus 10 - 20 rectis, inferioribus longioribus, centrali singulo breviore ; 
floribus lateralibus sordide rubellis ; baccis elongato-clavatis ; semini- 
bus parvis rugulosis fulvis.. 
Var. a. applanata (M. applanata, E. in PI. Lindh. 1850) : vertice 
applanato s. depresso, aculeis radialibus 15-22. 
Yar. /3. hemisphjerica (M. hemisphserica, E. 1. c.) : vertice con- 
vexo, aculeis radialibus 9 - 12. 
From San Antonio and New Braunfels, Texas, to Matamoras and 
westward to El Paso : fl. April, May. — Var. a. is the Northern and 
Western, and /3. the Southern form. — M. declivis , Dietr. seems to 
belong here ; but I have never met with a description of this plant. 
11. M. meiacantha, E. in B. C. R.: hemisphserica; tuberculis quad- 
rangulato-pyramidatis compressis ; aculeis paucis (5-9) rigidis rectis 
s. recurvatis, inferioribus paulo longioribus, centrali singulo erecto s. 
sursum flexo et cum cseteris radiante; floribus et baccis prsecedentis. 
Western Texas and New Mexico.— Very similar to the last; but 
tubercles larger, more compressed, more loosely arranged; the spines 
fewer and stouter; perhaps only a variety of it. 
