VARIATIONS OF GAKTER-SNAKES. 



115 



hand, is more variable than in eitlier of the other forms in the (rroiip. 

 An examination of the diagrams (figs. 46-47) will show that the 

 variation in both series consists of a loss or an addition of one scute 

 from the more constant number 7/10. The average number of 

 suj)ralabials is generally a little above 7, showing the comparative 



Fig. 46.— Diagram showing the variatio.n' in the number of supralahials in Thamnophis 



sauritus. 



lareness of specimens with S or 6 scutes in this series. No definite 

 geographic difTerences can be discovered in the material examined. 

 In the case of the infralabials the conditions are exactly reversed in 

 that, while the variations are so slight as to disturb the averages 



n 



10 



y^- 



f3' 



4,, 



-);- 



t:HS.=-^ 



5 



->() 



10 



land, kee, 



Veeders- Waterloo 



burg, Indiana. 

 Indiana. 



North ton,D.C., 

 Carolina. Laurel, 

 Mary- 

 land. 



Wheat- Maxiukuc- Oberlin, Washte- Carlisle, Avoca, Washing- Delaware 



Pemisyl- North ton,D.C., County, 

 vania. Carolina. Laurel, Pennsyl- 

 vania. 

 Pleasjint 

 Point, 

 Haddon- 

 fieldjNcw 

 Jersey. 

 s IN Tham: 



Medina naw, 

 County, Lapeer, 

 Ohio. Eaton, 

 and 



Gratiot 

 counties, 

 Michigan. 



Rhode 

 Island, 

 Massa- 

 chusetts, 

 Connecti- 

 cut. 



Fig. 47.— Diagram showing thk variation in tue numuer of infralahiai. 



sauritus. 



but little, the differences that do occur are mostly In^ way of a 

 reduction to 9, so that the averages run a little below 10. 



As in the other ribbon snakes, the variation in the number of 

 ventral plates is considerable. In the material examined the ex- 

 tremes are 150 and 172. The table (fig. 48) will show how the 



