Var. /?. c2espitosa (M. similis, E. in Pl.Lindh. 1845): caespitosa; 
aculeis radialibus 12-15 puberulis, centrali plerumque deficiente; 
floribus baccis seminibusque majoribus ; stigmatibus 5 patulis. 
Var. y. robustior, E. in PI. Lindh. 1850 : subsimplex ; tuberculis 
longioribus laxioribus, aculeis robustioribus laevibus, radialibus 10-12, 
centrali singulo ; floribus majoribus; stigmatibus 7-8 patulis; semini- 
bus ut in /3. 
Plains east of the Rocky and New Mexican Mountains. Var. a. on 
the Upper Missouri; (3 . from Kansas River to New Braunfels in Texas ; 
y. from the Canadian River to the Colorado of Texas. The heads 
are one or two inches in diameter; the csespitose masses of /3. often a 
foot broad ; spines 3 — 8 lines long. Flowers 1 — 2 inches long and 
wide, of a greenish or reddish or pure pale yellow color. Seeds 
0.8- 1.1 lines in diameter, more regularly globose than in most other 
Cactacae. 
16. M. Scheerii, Muhlenpf. 1847; 0. ? valida, E. in B. C. R.: 
magna, ovato-globosa, subsimplex, glaucescens; tuberculis remotis 
patulis magnis e basi lata subcylindricis supra sulco profundo glandu- 
lis paucis munito (juniore lanato) subbilobis ; areolis junioribus dense 
lanatis; aculeis 10- 20rectis robustis basi bulbosis albidis s. citrinis 
apice fuscatis, radialibus 9 - 16 ; centralibus 1-5 validioribus angu- 
latis ; floribus flavis ex axillis junioribus tomentosissimis. 
Sandy ridges in the valley of the Rio Grande near El Paso : fl. 
July. The largest of our Northern Mamillarise, 7 inches high and 5 
in diameter; tubercles 1-1| inches long; spines 10-18 lines in 
length, very stout, especially the central and lower radial ones. 
Flower 2 inches long, yellow. Fruit not seen .—M. Scheerii from 
Chihuahua, according to Prince Salm’s description, is a smaller plant, 
with single central spines one inch in length, and 8- 11 much shorter 
radial spines ; the areolse are described as naked : — nevertheless our 
plant is probably only the northern form of this species. 
17. M. robusti SPINA, A. Schott, in litt.: simplex s. cfespitosa; 
tuberculis patulis teretibus magnis sulcatis; areolis junioribus dense 
tomentosis ; aculeis radialibus 12-15 robustis inferioribus robustiori¬ 
bus saepe curvatis, superioribus rectis fasciculatis paullo tenuioribus, 
centrali singulo valido compresso recurvato, omnibus subpollicaribus 
corneis apice atratis ; floribus lute is ex axillis junioribus tomentosis? 
simis ; seminibus magnis obovatis fuscis laevibus. 
S,onora, on grassy prairies : fl. July. Tubercles nearly an inch 
