or ARTS AND SCIENCES. 313 



1. The Atlantic Region ; which has only a single Opuntia, and 

 that peculiar to it. Along the Southern coast some West Indian 

 species may yet be expected. 



2. The Mississippi Region, including the Western States, pro- 

 duces another Opu7itia, which, in difTerent distinct forms, extends into 

 the 3d, 4th, and 5th regions. 



3. The Missouri Region ; namely, the Northwestern or Upper 

 Missouri Territory to the Rocky Mountains. It furnishes 



Two Mamillaria of the subgenus Coryphantha, both extending into 

 the 4th and 5th region ; and 



Three Opuntia:, one of which only is peculiar. 



4. The Texan Region ; 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 MamillaricB, 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 Opu7itice, 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. The New-Mexican Region ; 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 MamiUarice, (eight EumamillaricB, ten Coryphanth<z, and 

 one Anhalonium), of which sixteen are peculiar; 



Nine EcJmiocacti, 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 OpimticB ; of these twelve are flat-jointed, four clavate, 

 and five cylindrical ones : seventeen of these species are peculiar. 



6. The Gila 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. 



VOL. III. 40 



