11 
inches in diameter. Lower tubercles 2 - 3, floriferous ones 5-6 lines 
long ; spines 3-5, upper fasciculated ones 6-9 lines long. Flower 
2| - 3 inches in diameter ; seed 0.9 line long. 
21. M. Echinus, E. 1. c. : simplex, globosa; tuberculis tereti-. 
conicis ; areolis orbiculatis ; aculeis rectis s. paullo curvatis intertextis 
albidis; radiantibus 16-30 summis paullo longioribus, centralibus 3- 
4, inferiore robustissimo subulato porrecto, superioribus 2 - 3 et cum 
radiantibus erectis; floribus magnis. 
With the former. — Plant 1J-2| inches in diameter; tubercles 
5-6 lines long; lower and lateral spines 4 - 6, upper ones 6-10 
lines long ; upper central spines of the same length, and the lower 
central one a little shorter. This last one is unusually stout, subulate 
from a very thick base, and perpendicular on the centre of the plant, 
which gives it a very peculiar aspect. Flowers apparently about 1£ 
or 2 inches long. 
22. M. scolymoides, Scheidw. (1841): globosa s. ovata, subsim- 
plex; tuberculis conicis, superioribus elongatis incurvis imbricatis ; 
aculeis radiantibus 14-20 rectis s. plerumque recurvis albidis s. cor- 
neis, superioribus longioribus, centralibus 1-4 longioribus obscuriori- 
bus curvatis, superioribus sursum versis cum radialibus implicatis, 
inferiore robustiore longiore decurvo. 
South of the Rio Grande ; not yet discovered in our territory. — 
Plant 2—3 inches high ; tubercles 5-8 lines long; radial spines 5~ 
10 lines, the central ones 9-16 lines long. Flowers yellow, 2 inches 
long. — Perhaps this and both the foregoing species are only forms of 
the Mexican M. cornifera, of De Candolle. Only a close examination 
of these plants in their native wilds will enable us to decide this point. 
23. M. calcarata, E. in PL Lindh. 2, 1850 (M. sulcata, E. in 
PI. Lindh. 1, 1845. M. strobiliformis, Muhlenjpf. ? non Scheer ) : glo¬ 
bosa, prolifera, csespitosa; tuberculis e basi dilatata ovatis conicis; 
aculeis albidis, radialibus 8-10 rigidis subulatis rectis s. paullo re¬ 
curvis, additis subinde ex summa areola aculeis adventitiis 3-5 fas- 
ciculatis tenuioribus, centrali singulo robustiore subulato recurvato, in 
plantis junioribus deficiente; floribus magnis sulphureis intus basi 
rubicundis. 
Texas, from the Brazos to the Nueces rivers: fl. May. — Larger 
heads 2 — 2£ inches in diameter; csespitose masses a foot or more 
large; tubercles spreading, or in older flowering plants often some¬ 
what adpressed and imbricate, 7-9 lines long; spines 4-8 lines 
