The species is closely allied to C. roseanus, but differs in its
shorter tubercles and much longer spines. About a dozen stems
rise in a clump, about a foot high, covering an area of 2 or 3
feet. These two species represent a very distinct Lower
Californian group of cylindrical and hooked Eumamillarias. Both
probably have showy scarlet flowers and may attain considerable
length when growing upon rock ledges so as to become pendent.
The specimens of C. setispinus from San Julio Canyon are from
younger parts and show but a single long and hooked central. The
San Borgia specimens show mostly 3 or 4 centrals, the lowest one
hooked and becoming remarkably long and often variously twisted
and curved. However, I can discover no difference except such as
may be due to age.

++ Central spines present and not hooked.
+ Central spines more than one, longer than the radials, which
are numerous, white and slender (capillary or bristle-like)
(rigid in C. Halei).

25. Cactus halei (Brandegee).

Mamillaria halei Brandegee, Proc. Calif. Acad. Sci Scr. 2. ii.
161 (1889).

Stems cylindrical, 8 to 10 in a clump, about 30 cm. high and 5 to
7.5 cm. in diameter: tubercles short, with axillary wool: radial
spines 10 to 22, rigid and erect-spreading, unequal, 6 to 15 mm.
long; central spines numerous and erect-spreading, 1 to 3 of them
very stout and prominent (25 to 35 mm. long); all the spines
straight, at first reddish-brown, becoming yellowish and ashy,