94 Proceedings of the Biological Society of Washington. 



the possible future revision of the genus, I think it well to name 

 the snake from San Luis Potosi, and it may be called 



Tantilla deviatrix sp. nov. 



Ti/pe, M. C. Z. No. 6195, from San Luis Potosi, Mexico, collected in 

 March, 1878, by Dr. Edward Palmer. 



Head narrow, not distinct from neck; eye rather small, scarcely more 

 than one third the length of the snout; rostral wider than high, the 

 portion visible from above less than the length of the internasal suture; 

 internasals short, less than half as large as the praefrontals, the lower 

 border of each of which is wedged down between the posterior nasal and 

 the praeocular, but not to contact with the supralabials ; frontal a hexa- 

 gon, the anterior angle very obtuse, the posterior rather acute, the side 

 borders converging very slightly backwards ; its width slightly more than 

 two thirds its length and about twice the width of the supraoculars, its 

 length slightly less than the interparietal suture; supraoculars moderate, 

 their width at the posterior end scarcely half that of the frontal ; parietals 

 slightly longer than their distance from tip of snout; nasals and prae- 

 ocular of about equal size, the latter considerably in contact with the 

 posterior nasal; one praeocular; two postoculars, the upper the larger; 

 temporals 1 + 1 (on one side, the left, of the type, there is a tiny scale 

 intercalated between the upper postoculars and the upper anterior corner 

 of the first temporal) ; temporals long and narrow; supralabials 7, third 

 and fourth entering the eye, seventh largest, almost square; infralabials 

 7, four in contact with anterior chin shields, first pair broadly in contact 

 with each other behind mental ; anterior chin shields slightly longer than 

 the second pair ; 15 rows of smooth scales ; four pairs of scales between 

 posterior chin shields and ventrals; ventrals 154; anal divided; sub- 

 caudals 63. 



Color (in alcohol) very pale uniform reddish above (evidently much 

 faded), yellowish white beneath; top of head brown, the dark color 

 barely including the eyes and descending to the labial margin on the 

 posterior half of the sixth and the entire seventh supralabial ; a white 

 semicollar just behind the parietals and taking in their posterior ends 

 (about one sixth of the parietals being white), in general the white band 

 covers a part of two rows of scales and it is followed posteriorly by a 

 narrow brown band only about one scale wide; the latter band extending 

 slightly and abruptly forward on the median line, thus narrowing the 

 white semicollar at this point. 



Total length, 170 mm., tail 39 mm. 



It is well to state here that Gunther says that T. bocourti has ventrals 

 172-176 and subcaudals 55, which is quite different from the count given 

 above, while Stejneger gives for T. wilcoxi a count of, ventrals 152, tail 

 imperfect. The size of eye, shape of head and arrangement of chin shields 

 sets deviatrix well oflf" from wilcoxi. A second specimen of T. wilcoxi 

 was recorded by Van Denburgh (Proc. Cal. Ac. Sci. (4), 3, 1913, p. 424) 

 from Ramsay Canon in the Huachuca Mountains of Arizona. This ex- 

 ample has 157 ventrals and 58 subcaudals. 



