800 13. COLUBRIDA 
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 parie- 
talis. 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, 7’. sirtalis infernalis, from the northern sub- 
species, 7". sirtalis concinnus. This difference in gastrosteges 
is clearly shown in Figure 1. 
