Vol. VIII] VAN DENBURGH AND SLEVIN— GARTER-SNAKES 



189 



1. Thamnophis sirtalis parietalis (Say) 



2. Thamnophis sirtalis concinnus (Hallowell) 



3. Thamnophis sirtalis infernalis (Blainville) 



While these three are the only western races of T. sirtalis 

 recognized in this review, it is far from certain that this num- 



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Figure 1 



Fig. 1. This chart shows the number of gastrosteges in specimens of 

 Thamnophis sirtalis concinnus, represented by a continuous line, and 

 Thamnophis sirtalis infernalis, represented by a broken line. The upper 

 half of the chart shows the counts in males, the lower half the counts in 

 females. The chart shows the percentage of the total number of speci- 

 mens of each sex having each number of gastrosteges, and brings out 

 clearly the fact that in T. s. infernalis these scutes are more numerous 

 than in T. s. concinnus. 



