PROCEEDINGS 



OF THE 



CALIFORNIA ACADEMY OF SCIENCES 



Fourth Series 



Vol. X, No. 1, pp. 1-27, pis. 1-2 August 6, 1920 



A FURTHER STUDY OF VARIATION IN THE 

 GOPHER-SNAKES OF WESTERN NORTH 



AMERICA 



BY 



JOHN VAN DENBURGH 



Curator, Department of Herpetology 



In August of last year the writer and Joseph R. Slevin pub- 

 lished the results of a study of some three hundred specimens 

 of Pitnophis from western North America^ Probably no one 

 who has not undertaken such a study can realize the amount of 

 time and effort necessary for gathering, analyzing, digesting, 

 and formulating the data derived from such a mass of material 

 as was involved in our earlier study of the garter-snakes of the 

 genus Thamnophis. The time and effort expended were so 

 great that in the subsequent study of Pitnophis the attempt was 

 made to reach conclusions without so much attention to detail. 

 The result was that, while the conclusions reached were valu- 

 able and probably correct, as far as they went, they never have 

 been satisfactory as a solution of the problems in variation and 

 distribution offered by this genus. Further study of the data 

 published in that paper indicated the probability tliat the snakes 



1 The Gopher-Snakes of Western North America. <Proc. Cal. Acad Sci 4th Ser 

 vol. 9, no. 6, pp. 197-220, pis. 11-13, August 21, 1919. ' '' 



August 6, 1920 



