184 CALIFORNIA ACADEMY OF SCIEXCBS [Proc. 4ih Ser. 



KEY TO THE GARTER-SNAKES OF WESTERN NORTH AMERICA 



a. — Lateral light stripe anteriorly not involving scales of the fourth row. 

 b. — Lateral stripe anteriorly upon scales of the second and third rows, 

 c. — Supralaljials normally seven. 



d. — Eye large, posterior genials much longer than anterior, 

 infralabials usually ten, scale-rows 19 — 19^17. 

 e. — Gastrosteges (146 to 170) and urosteecs (66 to 95) 

 average fewer in number (156-166 and 76 to 85). 

 f. — (Coloration lighter, with broader light lines. 



T. sirtalis parietalis p. 190 



f^ — ^Coloration usually darker both above and below, 

 lines often narrower. 



T. sirtalis concinnus p. 192 



el--Gastrosteges (156 to 177) and urosteges (74 to 97) 

 average more numerous (163 to 169 and 83 to 90), col- 

 oration lighter than in f^ 



T. sirtalis infemalis p. 198 



d'. — Eye much smaller, posterior genials about equal to anterior, 

 infralabials usually fewer than ten, scale-rows usually 17 — 

 17—15. 



T. ordinoides ordinoides p. 215 



c^ — Supralabials normally eight. 



dd. — Scales usually in not more than 19 rows. 



ee. — Gastrosteges average more than 160, eye large, pos- 

 terior genials longer. 



T. eques p. 204 



ee'. — ^Gastrosteges average fewer than 160, eye small, genials 

 subequal. 



T. ordinoides atratus p. 224 



dd^ — Scale usually in more than 19 rows. 



eee. — Dorsal line present over most of body. 



ff_ — Dorsal line very distinct with sharply defined bor- 

 ders not invaded by dorsal spots, little dark pigmen- 

 tation on gastrosteges. 



T. ordinoides elegans p. 235 



ff*. — Dorsal line with borders invaded by dorsal spots, 

 dark pigmentation of gastrosteges often present, 

 g. — Preocular single, dorsal spots and dark pigmen- 

 tation of gastrosteges usually very prominent. 



T. o. vagrans p. 240 



g^ — Usually two preoculars, dorsal spots and pig- 

 mentation of gastrosteges usually less evident. 



T. o. biscutatus p. 245 



eee^ — Dorsal line usually absent, or short, or indistinct, 

 fff. — Remnant of dorsal line usually present, preocular 

 single, infralabials often more than ten. 



T. o. couchii p. 251 



fff — No dorsal line, often more than one preocular, in- 

 fralabials rarely more than ten. 



gg. — Lateral lines usually present, dorsal spots fewer, 

 or absent. 



T. o. hammondii p. 256 



gg^. — Lateral lines usually absent, dorsal spots very 

 numerous and prominent. 



T. angustirostris p. 264 



b^ Lateral stripe anteriorly upon scales of the third row only, li!?ht 



postoral crescents present. 



T. marcianus p. 261 



a'. — Lateral light stripe anteriorly involving the scales of the fourth row 



T. megalops p. 263 



