57 
1. Tue Atiantic Recion ; which has only a single Opuntia, and 
that peculiar to it. Along the Southern coast some West Indian 
species may yet be expected. 
2. Tue Mississipr1 Recion, including the Western States, pro- 
duces another Opuntia, which, in different distinct forms, extends into 
the 3d, 4th, and 5th regions. 
3. THe Missouri Recion; namely, the Northwestern or Upper 
Missouri Territory to the Rocky Mountains. It furnis 
wo Mamillaria of the subgenus Coryphantha, both pores into 
the 4th and 5th region; and 
Three Opuntia, one of which only is peculiar. 
4. Tue Texan Recon; namely, the eastern and inhabited parts of 
Texas, westward to the San Pedro, and northward including the terri- 
tory south of the Arkansas River. This region produces 
Five Mamiillaria, two of them peculiar to this district ; 
Three Echinocacti, none of which are found in any other of our 
regions ; 
Six Cerei (five Echinocerei and one Eucereus), all of them pecu- 
liar to this district ; and 
Six Opuntia, of which only three are restricted to it; among them 
is only a single cylindric Opuntia. 
This region contains therefore altogether twenty species, fourteen 
of which are peculiar to it. 
5. Toe New-Mexican Recion; namely, Western, uninhabited, 
mountainous Texas, and Eastern New Mexico to the eastern head- 
waters of the Colorado of California. This region is our richest 
Cactus district. It has furnished sixty-five species, fifty-five of which 
are peculiar to it, viz. : — 
Nineteen Mamillarie (eight Eumamillaria, ten Coryphanthe, and 
one Anhalonium), of which sixteen are peculiar ; 
' Nine Echinocacti, all of them belonging to this district only ; 
Sixteen Cerei (fifteen Echinocerei, fourteen of which are peculiar, 
and one Eucereus, common also to other regions) ; and 
Twenty-two Opuntia ; of these twelve are flat-jointed, fout clavate, 
and five cylindrical ones : seventeen of these species are peculiar. 
Tue Gita Region, comprising the whole valley of the Colorado 
* Always excepting Mexico itself, south of the Rio Grande, into which many, if 
not most, of our species extend 
