R. Zweifel 1953 Thamnophis [illegible] errans 7 mi SW El Vergel (Jaguneta) 7800', Chihuahua, Mexico 2273-4 RZ June 29, These snakes have a yellow dorsal stripe and reddish-brown venter (excepting the pale yellow chin). Of four taken so far, only one was near the water; the others in the dry pine forest. July 1 2303 RZ Under a log in pine forest far from water. This species has a tongue which is all black in life. 2340 RZ July 3 A newly born individual doesn't have the reddish- brrown venter, but the all black tongue still serves to distinguish it from T. cyrtoptis which it otherwise rather resembles.