14 UNITED STATES AND MEXICAN BOUNDARY. 
from the Pecos have very straight central spines; but some from Presidio del Norte, not other- 
wise different, have somewhat recurved and darker horn-colored central spines. 
17. M. sconymorpss, Scheidw. ; a small slender-spined form was collected by Mr. Wright on 
the Pecos, and by Dr. Bigelow about Santa Rosa. Tubercles compressed, incurved, imbricated ; 
radial spines on the upper ones about 20, with 4 longer and darker incurved central ones, the 
upper ones bent upwards and almost mixed with the upper radial ones; lower one mostly over 
an inch long. This species and the two preceding may possibly be forms of De Candolle’s 
M. cornifera. 
18. M. catcarata, E. in Pl. Lindh., has been collected by Mr. Wright as far west as the 
Nueces river. His specimens have only 8 or 10 radial spines, 4-6 lines long; central spine of 
the same length, but stouter, often (in young specimens?) entirely wanting. Lindheimer’s 
original specimens from the neighborhood of the Colorado and Guadalupe rivers, have 10-12 
radial spines 8-9 lines long; central spine stouter but shorter, sometimes wanting; seeds 
similar to that of M. pectinata, but larger and very obtuse at base; 1-1, 2 lines long. (Tab. 
LXXIV, fig. 1.) 
19. M. TuBERcuLOsA (sp. nov.): ovata seu ovato-cylindrica, simplex seu ad basin ramosa; 
tuberculis e basi rhomboidea ovatis abbreviatis obtusis, subcompressis, profunde usque ad axil- 
lam villosissimam sulco villoso exaratis confertis imbricatis, demum nudatis suberosis persisten- 
tibus; areolis orbiculatis, novellis albo-tomentosis ; aculeis exterioribus 20-30 rigidis gracilibus 
albidis nunc apice sphacelatis radiantibus intertextis, interioribus 5-9 robustioribus sursum 
cesio-purpureis apice sphacelatis, quorum superiores longiores erecti versus caulis apicem in 
comam aggregati, inferior brevior robustus porrectus deflexusve ; floribus in vertice densissime 
tomentoso centralibus pollicaribus dilute roseis ; sepalis 16-18 lanceolatis arachnoideo-fimbria- 
tis; petalis 10-13 lineari-lanceolatis aristatis subintegris ; bacca ovata elongata floris rudi- 
mentis breviter convolutis coronata rubra; seminibus subgloboso-obovatis scrobiculatis fuscis, 
hilo ovato minuto ventrali. (Tab. X., fig. 1—6.) 
From the Pecos to Leon springs, Eagle spring, and El Paso, on the higher mountains, 
Wright ; especially on the rocky summits of the “‘ Flounce mountains,’ below El Paso, Bige- 
low: fl. in May and June.—A very pretty and well defined species of the mountain region. 
Stems 2-5 inches high, 1-2 inches in diameter, often with globose branches at the base : tubercles 
mostly only 3 lines long, and of the same width at base, often shorter, rarely and ahily in very 
vigorous plants 4 or even 5 lines long; in 13, or on the lower part of old plants in 21, spiral 
rows, like the whole body of the plant, of a corky texture and substance, almost dry, and there- 
fore not shrivelling when old, but after shedding the spines, persistent and covering the older 
parts of the stem as grey, corky tuberosities, whence the name. The deep, densely woolly groove, 
and the very woolly axilla, which loses its coating only after several years, are quite peculiar 
to this species. Radial spines usually 22-26, rarely less than 20, and never in the numerous 
specimens examined by me more than 30, very slender but stiff, usually 2-4 lines long, lower 
and a few upper ones 2 lines, most upper ones 3-4 lines long, uppermost rarely 5 or even 6 lines 
in length ; lower stout central spine 3-4, upper ones 5-7, and in a few specimens even 8 or 9 
lines long ; those of the uppermost tubercles crowded together, erect, forming a purplish grey 
taft, which surrounds and partly hides flowers and fruit, Flowers very pale purple, about one 
inch in diameter ; berry oval, elongated, and sometimes almost cylindric, red, vind by both 
these characters distinguished from the fruit of the allied. species ; remai ns of flower not irregu- 
