68 BULLETIN 114, UNITED STATES NATIONAL MUSEUM. 



of hoylii. It would be interesting to know how severe desert condi- 

 tions it can withstand, and whether it differs in this respect from 

 hoylii. It may be a long time before the natural history of the various 

 forms of the getulus group is well known, but, when it is, we shall 

 expect to be able to trace courses of evolution in habits correspond- 

 ing with and bearing out the observations on the structural evolution 

 of the group. 



Range. — This form inhabits the desert region of the southern third 

 of Arizona (except the extreme southeastern corner), the Colorado 

 Desert, and the area about the head of the Gulf of California. 



Specimens are in the coEection of the National Museum from Ash 

 Creek in the Graham Mo im tains, Arizona, at 3,200 feet elevation 

 (evident!}^ the base of the mountains) and from Fort Grant and 

 Calva in Graham County. It will be interesting to learn whether 

 this form extends up the Gila Kiver and its branches into New Mex- 

 ico, and to see if the divide between the Colorado drainage system 

 and the Rio Grande proves to be also the divide between this form 

 and splendida. If this proves to be the case, it will be a matter of no 

 small interest to see if these two forms are sharply distinct here. 

 This is to be expected, since none of the members of this group are 

 known to inhabit actually mountainous regions. Enough specimens 

 are available from the vicinity of Tucson to show that this is a region 

 of intergradation between splendida and yumensis. From the topog- 

 raphy of the coimtry it may be expected that yumensis ranges south 

 on the east coast of the Gulf of California to the region of the twenty- 

 eighth parallel, perhaps farther. West of the Colorado Eiver, except 

 for the vicinity of Yimia, the only record is for Volcano Lake, Lower 

 California, near the delta of the Colorado River, at the east base of 

 the Cocopah Mountains. West of the Yuma region it is assumed that 

 the range of yumensis extends throughout the Colorado Desert, since 

 specimens from western San Diego County strongly suggest deriva- 

 tion from yumensis. South into Lower California its range is probably 

 limited by the region where the mountains reach the east coast, at 

 about the thirty-first parallel. Specimens in the United States 

 National Museum from the northwest coast of Lower California and 

 from San Pedro Martir Mountain, Lower California, are distinctly 

 hoylii. 



Specimens have been examined from the following localities, in 

 addition to those represented by specimens in the United States 

 National Museum: Tucson, Fort Grant, and 10 miles below Cibola in 

 Yuma Coimty, Arizona; ^^Sonora" (southern Arizona); Pilot Eaiob 

 (Imperial Coimty), California. 



There seem to be no published records for other localities than 

 these. 



