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the mountains of southeastern California, and extended through west- 
ern Arizona to southern Nevada and southern Utah, the most extended 
northern range of any EUMAMILLARIA. The twelfth form, goodrichit, 
is Lower Californian, and extends into California only in San Diego 
Jounty. A summarized statement of the distribution of our twelve 
KUMAMILLARL& would be that two of them have extended from the 
low grounds of Coahuila and Chihuahua and spread along the valley 
of the Rio Grande; nine have come from the high grounds of Chihu- 
ahua and Sonora, four of which have extended eastward to the low 
levels of southeastern Texas; four have kept to the highlands west of 
the Pecos, and one has kept to the Colorado Valley and its tributaries, 
while one has a short northern extension from Lower California. 
The nineteen forms of CORYPHANTHA are decidedly more northern 
in their distribution, and are our characteristic representatives of the 
genus Cactus. Ten of these, however, are but northern extensions of 
Mexican forms, and six of the ten have simply that tongue-like northern 
extension in the mountains between the Pecos and the Upper Rio 
Grande (above El Paso), viz.: dasyacanthus, tuberculosus, scheerit (which 
has also spread somewhat east of the Pecos), and the three pectinate 
and closely related forms radians, echinus, and scolymoides. Of the four 
remaining Mexican forms, macromeris is a low ground Rio Grande Val- 
ley form, extending from above El Paso well towards the Lower Rio 
Grande; potsii just crosses the border in the neighborhood of Laredo; 
and radiosus and neo-mevicanus have by far the greatest northern exten- 
sion, stretching from Sonora and Chihuahua to southern Utah and cen- 
tral Colorado, and eastward to the Guadalupe River of Texas. 
The nine remaining coryphanths are distinctly forms of the United 
States, occupying two well-marked regions, viz.: the northern plains, 
and the desert region of western Arizona and adjacent California, Ne- 
vada, and Utah. In the former region is found the widespread vivi- 
parus, Which extends from the southern borders of British America to 
the plains of eastern Colorado and western Kansas, and even crosses 
the Rocky Mountain divide into northern Idaho and northeastern Wash- 
ington; and missouriensis, which also ranges from the high prairies of 
the Upper Missouri to the same southern limit, and is continued south- 
ward into Texas in its varieties similis and robustior. 
In the Arizona desert region, four distinct but closely allied forms 
have become differentiated from the strong radiosus stock, viz.: arizoni- 
cus, deserti, alversont, and chloranthus, all of which might be regarded 
as distinct species. In southeastern Texas is found an isolated form, 
sulcatus, occuring between the Brazos and Nueces rivers. That vivi- 
parus must be regarded as a strong northern extension of the radiosus 
stock can not be doubted, as the low depressed cespitose northern form 
seems to merge southward so gradually into the simple more robust 
ovate to cylindrical forms of radiosus as to suggest the propriety of 
regarding them all as specifically identical. 
