VARIATIONS OF GARTER-SNAKES. 



117 



differences in color have been observed which are evidently geo- 

 graphic.) 



If the data plotted can be depended upon to reveal the actual 

 state of variation, the form may thus be divided into two sections 

 upon the basis of the scutellation and tail length, i. e., a trans- 

 Allegheny section characterized by a larger number of ventral scutes, 

 a shorter tail and fewer subcaudal scutes, and a coastal plain section 

 characterized by a fewer number of ventral plates, a longer tail and 

 more subcaudal scutes. 



143 



135 

 121 

 119 

 111 



103 

 95 

 8T 



Fig. 50.- 



-PlAGRAM SHOWING THE VARIATION IN THE NUMBER OF SUBCAUDAL SCUTES IN TlIAMNOPHIS 



SAURITUS. 



AJJinities. — -The position of the lateral stripe (on the third and 

 fourth rows) and the long tail justifies us in placing smiritns in the 

 same group with sackeni and proximus. As has been shown, it meets 

 the range of sackeni in the latitude of northern Florida and that of 

 proximus along the eastern boundary of Illinois and in western Ken- 

 tucky, Tennessee, and Mississippi. Specimens from the intermediate 

 region along the common boundaries of the three forms remain to be 

 examined, but I believe that there can be no doubt that sauritvs 

 intergrades perfectly with both sackeni and proximus. 

 33553— Bull. 61—08 9 



