10 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



I have called a summation of characters. Individual variation 

 in any one specimen rarely affects greatly all of the characters 

 involved in geographic variation. Therefore, by adding to- 

 gether, or subtracting various characters showing geographic 

 differences, the factors of individual variation are proportion- 

 ally reduced or buried, and geographical variations are less 

 concealed. 



Figure 7 represents this principle as applied to certain charac- 

 ters of the gopher-snakes. The number of dorsal and caudal 

 blotches together has been subtracted from the number of gas- 

 trosteges for each specimen. Certain differences between the 

 subspecies become at once evident. P. c. annectens (curve 3) 

 stands out as very distinct from P. c. deserticola (4) and the 

 snakes of Arizona and Utah (5 and 6). P. c. heermanni (2) is 

 also clearly different from P. c. deserticola (4). The Arizona 

 snakes (6) plainly are not like those of Utah (5), nor like the 

 Lower Californian P. vertehralis (curve 7). 



Still other differences between various subspecies exist but 

 have not been charted. Thus, the snakes of Utah and Arizona 

 most frequently have but one preocular, vr'hile the other races 

 usually have two. In P. vertehralis the supralabials usually are 

 nine, while eight is the number most frequent in the other races. 



It seems, then, that instead of the three kinds of gopher- 

 snakes which have been recognized by authors for many years, 

 the facts will be best set forth by according recognition to seven 

 kinds from western North America. The chief differences be- 

 tween these may be briefly set forth in the following table of 

 averages. The complete scale-counts and localities are given 

 in the earlier paper. The counts of the blotches are given here 

 under the head of each subspecies with the numbers of the 

 specimens and of the localities as in the former paper. 



