800 13. COLUBRIDM 



recognition of concinnus as a subspecies distinct from 

 parietalis. 



T. sirtalis concinnus differs from T. sirtalis infernalis 

 in coloration in the same respects as from T. sirtalis -pane- 

 tails. It also differs from T. sirtalis infernalis in having a 

 smaller number of gastrosteges and urosteges. 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 

 difference 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 sepa- 

 rate the sexes, for the females have much lower counts 

 than the males. The average count in males from Wash- 

 ington is 245.5, the average in males from central and 

 southern California ranges from 255 to 265; the extremes 

 of variation in the latter area being 251 and 270, while in 

 Washington specimens they are only 239 and 250. Similar 

 differences are found in the counts of female specimens, the 

 Washington average being 230.1, as against central and 

 southern California averages of from 243.7 to 248. Inter- 

 mediate localities show some intermediate counts, but in 

 general it may be seen that the difference is quite great and 

 constant enough to serve well for the separation of a south- 

 western race, T. sirtalis infernalis, from the northern sub- 

 species, T, sirtalis concinnus. This difference in gastrosteges 

 is clearly shown in Figure 1. 



