54 UNITED STATES AND MEXICAN BOUNDARY. 
with very numerous and long spines, spreading largely and growing 6-12 inches high; forminga 
welcome retreat for the smaller Rodentia, snakes, &c., which, under the protection of its pow- 
erful spines, are secure against the attacks of their enemies. Joints curved, 4-6 inches long, 
1-14 inch in diameter; the tubercles are 1-14 inch long, very prominent, and might 
be termed cylindric if they were not longitudinally attached to the stems. The upper 
tubercles of each joint and their spines are more fully developed than the others in this, as in 
all Opuntie. In those we distinguish four larger central spines; the upper one more erect, the 
lower one stouter, longer, broader, and deflexed. We often find a second upper one above, and 
a second lower one below the other, or the four central spines are surrounded by a circle of 6 or 
8 somewhat smaller spines, which may be considered as an interior series of radiating ones. 
The exterior series consists of 10-20 shorter and more slender spines ; but the arrangement of 
spines in this genus is never so regular as it is in other genera, especially in Echinocactus. 
Stoutest spines 14-24 inches in length, 3-1 line wide, striated, flat on the upper, strongly 
earinate on the lower surface, so as to appear triangular; other interior spines 1-2 inches, 
exterior ones $-1} inch long. Fruit 2-24 inches long, an inch in diameter ; larger pul- 
villis 2-23 lines in diameter; bristles whitish or reddish 3-4 lines long; 10 or 12 spines, 
4-8 lines in length, are mixed with the bristles on all or only on the lower pulvilli. Seeds in the 
same fruit 2-3 lines in diameter, or more; often transverse, or angular, blunt or beaked; 
cotyledons generally oblique, sometimes accumbent, contrary to the usual arrangement in this 
genus. The specimens from the lower Gila and the Colorado must, I have little doubt, also 
be referred here. Plant 12-18 inches high, far-spreading, of a duli greyish-green color ; joints 
similar to those described above; spines only 1-14 inch long; flowers sulphur-yellow, exter- 
nally tinged with purple, 2 or 24 inches in diameter; pulvilli of the ovary over a line in diam- 
eter, white-tomentose, supported by subulate leaves (2 lines long), bearing short white bristles 
and reddish spines ; exterior sepals oblanceolate, cuspidate, red-brown; interior ones with yellow — 
and red petaloid margins; petals yellow, with red tips; fruit not as large, but even more spiny 
than in the specimens from El Paso. This species, also, has been named in honor of Col. Wm. 
H, Emory, who, in his different expeditions to the extreme southwestern parts of our territory, 
always exerted himself for the advancement of our knowledge of the natural history of these 
regions. 
14. O. Scnorrm (sp. nov.): articulis breviter clavatis adscendentibus ; tuberculis elongatis ; 
pulvillis paucisetosis ; aculeis scaberrimis rubellis, interioribus 4 cruciatis, superiore triangu- 
lato erecto, caeteris ancipitibus supra planis subtus convexis, inferiore latiore; aculeis exterioribus 
8-10 radiantibus valde inequalibus; bacca ovata clavata pulvillis 35-40 setas suberectas 
aculeosque paucos gerentibus; seminibus angulatis rostratis transversis, commissura lineari 
indistincta. (Tab. LXXIII, fig. 1-3.) 
Abundant on the arid hills near the Rio Grande, between the San Pedro and Pecos rivers, 
Wright, Schott.—The specimens gathered in July and September were all in fruit. Joints 2 
inches, tubercles 8-9 lines long ; pulvilli even in the oldest joints with few bristles; spines 
rougher than in any other allied species, red ; the broader ones with a white margin, 14—2 inches 
long ; smaller radiating spines 4-9 lines long, almost surrounding the inner one. Ovary with 
white-tomentose pulvilli and short bristles ; those in the fruit become a little longer, but are 
confined to the upper half of the pulvillus and are erect, while in all the allied species they are 
much more numerous and stellately spread in all directions. Seed a little over 2 lines in the 
