Vol. VIII] VAN DENBURGH AND SLEVIN— GARTER-SNAKES 



187 



the dorsal line these characters are sufficiently constant to serve 

 for the recognition of concinnus as a subspecies distinct from 

 parietalis. 



As we pass south and east from the range of concinnus in 

 California and southern Oregon we find a definite increase in 

 the number of ventral plates. The snakes from the northwest 

 coast have fewer gastrosteges and urosteges than the snakes 

 from farther south and east in California. The greater differ- 

 ence is in the gastrostege counts, and these might perhaps be 

 used alone, but the combination of gastrostege and urostege 

 counts helps to bury individual variation. In a comparison of 

 this kind it is, of course, necessary to separate the sexes, for the 

 females have much lower counts than the males. 



The following table shows these counts in specimens from 

 many localities : 



Table of combined gastrostege and urostege counts 



