146 BULLETIN 175, UNITED STATES NATIONAL MUSEUM 



fauna, since only four specimens are considered, and the range of varia- 

 tion is well within the extremes for the subspecies as a whole. A 

 general tendency toward decrease in the sum of ventrals and caudals 

 from south to north is observable. The numbers of oculars and labials 

 are also very constant throughout the wide range of this form, and the 



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Region No. 1 2 3 4 5 6 7 8 9 10 



FiGUEE 65.— Geographic variation iu number of scale rows in Pituophis catenifer catenijer. 



only variation of any apparent significance is a slight general decrease 

 in the number of infralabials from south to north (fig. 6S). The 

 proportionate tail length shows no variation that seems to be of 

 geographic significance (fig. 69). 



