1914] Grinnell: Mammals and Birds of the Colorado Valley 101 



Rodents in which the Colorado River Acts as an Absolute Barrier 



Association 



Arizona side 



Encelia and I Ammospermophilus 



Rocky Creosote ) harrisi harrisi 



Sandv Creosote 



[ Thomorays chryso- 



Encelia and (Perognathus in- 



Rocky Creosote j termedius 



Ammospermophilus ) Encelia and 

 leucurus leucurus (Rockv Creosote 



Peromyscus crin- 

 itus stephensi 



California side 



Association 



Thomomys albatus > Saltbush 



Perognathus for- ) Encelia and 



mosus (Rockv Creosote 



Perognathus spina- ) Encelia and 

 atus spinatus (Rocky Creosote 



Rodents which Occur on Both Sides op the Colorado River, but which Show 

 Slight, Almost Impalpable, Differences on the Two Sides 



Citellus tereticaudus tereticaudus 

 Dipodomys deserti deserti 

 Perognathus penicillatus penicillatus 



Association 

 Sandy Creosote and Saltbush 

 Sandy Creosote and Saltbush 

 Saltbush and Sandv Creosote 



Rodents which are Apparently Identical on the Two Sides of the Colorado 

 River 



Castor canadensis frondator 

 Peromyscus maniculatus sonoriensis 

 Peromyscus eremicus eremicus 

 Sigmodon hispidus eremicus 

 Reithrodontomys megalotis deserti 

 Neotoma albigula venusta 

 Neotoma intermedia desertorum 

 Ondatra zibethica pallida 

 Dipodomys merriami merriami 

 Perognathus bombycinus 

 Lepus californicus deserticola 

 Sylvilagus auduboni arizonae 



Association 

 River 



All Riparian 



Saltbush and Sandy Creosote 

 Willow and Tule 

 Tule and Willow 

 Mesquite and other Riparian 

 Encelia 

 River 



Saltbush and Sandy Creosote 

 Sandy Creosote 

 Creosote and Saltbush 

 Quailbrush and Mesquite 



