116 



BULLETIN 61^ UNITED STATES NATIONAL MUSEUM. 



variations are distributed. While this diagram is very subject to 

 error, owing to the small number of specimens, it is interesting 

 to note that specimens from eastern localities have apparently a 

 smaller numl)er of ventral scutes than those from Michigan, Ohio, 

 and Indiana, and while larger suites of specimens will undoubtedly 



114 



166 



158 



150 



^ii 



15 



Ai- 



^^^^ 



10 



Fig. 48.— Diagram showing the variation in the number of ventral scutes in Thamnophis 



sauritus. 



change the averages, we believe that the difference is a real one. 

 The length of tail (fig. 49) is apparently quite constant. The ex- 

 tremes are .29 to .36, the average about .33, and while the average 

 can not be relied upon, it may be significant that the tail length is 



.^1 



U-^--. 



29 



Wheat- 

 land, 

 Veeders- 

 burg, 

 Indiana. 



-Si 



Maxinkuc- Oberlin, Washte- Carlisle, Avoca, Washing- Delaware Rhode 



kee, Medina naw, Pennsyl- North 



Waterloo, County, Lapeer, vania 

 Indiana. Ohio. Eaton, 



and 



Gratiot 



counties, 



Michigan. 



Carolina. Laurel, 

 Mary- 

 land. 



ton, D.C, County, Island, 

 Pennsyl- Massa- 

 vania. chusetts. 

 Pleasant Connccti- 

 Point, cut. 

 lladdon- 

 fleld,]Sew 

 Jersey. 



Fig. 49.— Diagram showing the variation in the proportionate tail length in Thamnophis 



sauritus. 



somewhat greater in eastern localities. This is shown better in the 

 number of subcaudal plates (fig. 50). Thus, in Ohio, Michigan, and 

 Indiana the extreme number of subcaudal plates is 87 and 121, the 

 averages between 100 and 117, while along the coastal plain the 

 extremes are 103 and 137, the averages between 115 and 120. (No 



