1913] Atsatt: Reptiles of tht San Jacinto Area 47 



especially through the San Gorgonio Pass and at the opposite end of 

 the area around Dos Palmos, where the two come together. The inter- 

 relations of these faunas in the cases of birds and mammals and some 

 of the laws governing behavior of races on the margins of two faunas 

 have been discussed in a preceding paper by Grinnell and Swart h 

 (1913). 



In a tabulation of the reptiles of the San Jacinto area in regard 

 to faunal distribution I find somewhat the same groups. (1) Some 

 species occur in both faunas, (2) some occur in one or the other fauna 

 only, and (3) some occur mainly in one fauna but invade the other 

 faunal area. In this third group the species invading one fauna 

 from the other fall into two sections. In one section (a) the species 

 invade the other faunal area for a short distance only, extending 

 about to Cabezon from either end of the San Gorgonio Pass. The 

 other section (b) contains species which invade for longer distances 

 and at both ends of the area, passing from either direction through 

 the entire length of San Gorgonio Pass and also pushing in from 

 either direction in the region around Dos Palmos. The larger part 

 of the invasion in this third group occurs in the San Diegan forms, 

 which go over the ridge and range down upon the desert side. The 

 invasion of all the species is along continuous associations of vegeta- 

 tion, but the two desert forms. Callisaurus ventralis and Crotaphytus 

 wislizenii, occur also in the isolated association or desert "island" at 

 Vallevista. Table II details the faunal distribution of species. 



The representation in the two faunas by a species in one and a 

 species, sub-species, or race, in the other does not attract one's atten- 

 tion in considering the reptiles of this area except in two cases. 

 Sceloporus magister and Sceloporus orcutti are closely related species, 

 the one in the Colorado and the other in the San Diegan fauna. 

 Around Snow Creek and Dos Palmos the two inhabit the same geo- 

 graphical area but maintain here their specific identity. The expla- 

 nation of this would seem to me to rest in the fact that they inhabit 

 different associations of vegetation. However, the Sceloporus orcutti 

 of the San Jacinto Region in general shows a greater degree of keeling 

 on the doi-sal scales, thereby approaching S. magister, than does S. 

 orcutti of other regions. The second case is that of Cnemidophorus 

 tigris and C. stejnegeri. C. tigris is reported from Palm Springs 

 (Stone, 1911, p. 231) and occurs eastward on the desert. C. stejnegeri 

 was found on the western side and through the Pass to Snow Creek. 

 The ranges of the two species probably meet near Snow Creek. At 



