(Eumamillaria and Coryphantha) deserve generic separation, for
the character of grooveless and grooved tubercles seems to hold
without exception, and the sections are separated with more
certainty than are certain species of Coryphantha and
Echinocactus. If genera are simply groups of convenience the
separation should be made.

I. EUMAMILLARIA. Flowers from the axils of the older or
full-grown tubercles (hence usually appearing lateral), mostly
small, and generally from whitish to pink or red: tubercles never
grooved: fruit almost always clavate and scarlet.

A. Tubercles more or less quadrangular.

* Central spines not hooked.
+ More than one central spine.


1. Cactus alternatus, sp. nov.

Subglobose, 10 cm. in diameter, simple: tubercles long (15 to 20
mm.) and spreading, with woolly axils: radial spines 3, rigid and
recurved, 5 mm. long; central spines 3, very stout and much
recurved, 20 to 30 mm. long, alternating with the radials; all
ashy colored and often twisted: flower and fruit unknown.--Type
in Herb. Coulter.

The few spines, with the very short radials alternating with the
very long and stout centrals, furnish a striking character.
Occasionally one of the centrals is wanting.