+0. THAMNOPHIS 853 



Thamnophis megalops Ruthven, Bull. U. S. Nat. Mus., No. 6i, 1908, 

 p. 44; Van Denburgh & Slevin, Proc. Cal. Acad. Sci., Ser. 4, 

 Vol. Ill, 1913, p. 421; Stejneger & Barbour, Check List N. 

 Amer. Amph. Rept., 1917, p. 101 ; Van Denburgh & Slevin, 

 Proc. Cal. Acad. Sci., Ser. 4, Vol. VIII, 1918, p. 283, pi. 15. 



Description. — Head distinct from neck, flat-topped, 

 with narrow, rounded snout, and temporal regions not in- 

 frequently swollen. Eye large. Rostral large, bounded 

 behind by internasal, anterior nasal, and first labial plates. 

 Plates on top of head: a pair of internasals, a pair of pre- 

 frontals, a frontal, supraocular of each side, and a p;ur of 

 parietals. Anterior and posterior nasals distinct. One 

 loreal. One preocular, and three or four postoculars. Tem- 

 porals one followed by two or three. Eight (rarely nine) 

 superior and 1 (rarely nine or 1 1 ) inferior labials, sixth 

 in each series usually largest, fourth and fifth superior reach- 

 ing eye, first pair of inferior meeting on median line. Two 

 pairs of genials, the posterior usually longer than anterior. 

 Scales on body in 21, or rarely 23, rows. Anal plate not 

 divided. Gastrosteges in Arizonan specimens varying in 

 number from 154 to 165. Urosteges in two series of from 

 72 to 77. 



The color above is olive or brown with three more or less 

 distinct longitudinal light lines. The dorsal line varies 

 considerably in width. The lateral line is on the scales of the 

 third and fourth rows anteriorly, of the third or second and 

 third posteriorly. Specimens with a light ground color show, 

 more or less definitely, two series of dark spots between the 

 dorsal and lateral lines, the spots of the upper series rather 

 more indefinite than those of the lower, with which they 

 alternate. In dark specimens these may be obscured. The 

 longitudinal lines are yellow or yellowish white. Dark 

 nuchal blotches are present. The labials are light olive or 

 yellow with dark posterior edges. A light postoral crescent 



