48 University of California Publications in Zoology [Vol. 12 



Snow Creek were captured specimens referred by me to C. stejnegeri 

 but which varied little from C. tigris. It seems probable to me that in 

 these two species we may have an illustration of the development 

 through the modifying influences of light, temperature, and humidity 

 of characteristics which have been described in specimens from widely 

 separated areas and given the standing of specific characters. Where, 

 however, these two have come into a common environment these specific 

 differences have become less pronounced. 



TABLE II 



1. Species occurring in both Colorado and San Diegan faunas. 



Uta stansburiana Salvadora grahamiae 



Bascanion flagellura frenatum ( .' | h'hinocheilus lecontei 



2. Species occurring in one fauna and not invading the other: 



Colorado Fauna San Dictum Fauna 



Sauromelas ater Verticaria hyperythra beldingi 



Sceloporus magister Eumeces skiltonianus 



Phrynosoma platyrhinos Pituophis catenifer 



( 'rotalus cerastes Diadophis amabilis 



3. Species passing from one fauna into the other: 



From Colorado into San Diegan From San Diegan into Colorado 



(a. Invading San Gorgonio Pass a short distance) : 

 Callisauros ventralis Phrynosoma blainvillei blainvillei 



( 'rotaphytus collaris baileyi Gerrhonotus scincicauda ignavus 



Crotaphytus wislizenii Lampropeltis boylei 



Uta mearnsi Bascanion laterale 



Crotalus lucifer 



(6. Invading entire length of San Gorgonio Pass and also around Dos Palmos): 

 < 'rotalus mitchelli Sceloporus biseriatus 



Sceloporus oreutti 

 Cnemidophorus stejnegeri 

 Lichanura roseofusca 

 Thamnophis hammondi 

 Crotalus ruber 



The San Jacinto mountains are separated from the San Bernar- 

 dino mountains merely by a narrow pass of Lower Sonoran character, 

 from three to five miles in width. Most of the San Jacinto and San 

 Bernardino species, as might be expected, are identical, yet we find 

 in the San Jacintos as characteristic of that region and not appearing 

 in the San Bernardinos (Grinned. 1908, pp. 160-170) the following 



