XII LIST OF ILLUSTRATIONS. 



Fig. 77. Forests in the Porcupine Mountains, Michigan I77 



78. Distribution of Thamnophis sirtalis, as indicated by the locality records. 180 



79. Variation in the number of supralabials in 113 specimens of Tham- 



nophis sirtalis from southeastern Michigan jg2 



80. Variation in the number of infralabials in 113 specimens of Thamnophis 



sirtalis from southeastern Michigan 1 00 



81. Diagram showing the variation in the number of ventral scutes in 

 Thamnophis sirtalis ^ j,o 



Phylogenetic development of the Sirtalis group 186 



82. 



