VAKIATIONS OF GARTER-SNAKES. 



183 



that it is frequently impossible to refer a specimen definitely to 

 either form. Nevertheless, while its range is not distinct from that 



Percentage of 

 specimens. 



.98 

 .82 

 .66 

 .50 

 .5 A 

 .18 



•^^11-71 11-10 10-10 10-9 9-3 8-8 



Infralabials. 

 Fig. 80.— Variation in the number of infralabials in 113 specimens of Thamnophis sirtalis 



FROM southeastern MICHIGAN. 



of sirtalis, it must be pointed out that the majority of the specimens 

 examined hail from northeastern United States (east of Ohio and 



170 



16 9 

 154 

 146 

 138 



Illinois. Southern Northern Indiana. Ohio. Florida. Maryland. Massa- Khodc 

 Michigan. Michigan. chusetts. Island 



Fig. 81.— Diagram showing the variation in the number of ventral scutes in- Thamnophis 



sirtalis. 



north of North Carolina), those from outside of this region being but 

 scattered records. 



