82 UNIVERSITY OF COLORADO STUDIES 



JJ. Dorsal parts not green ; general color gray, brown- 

 ish or reddish. . . Chionactis Cope (page ioo). 

 II. Nasal plates, two on each side. 



K. Maxillary teeth subequal; scales smooth; size 

 small ; dorsal parts uniform ashy brown to bluish 

 black; with or without yellowish red collar; ven- 

 tral parts orange or red. 



Diadophis Baird and Girard (page 101). 

 KK. Posterior maxillary teeth longer than those in 

 front; scales smooth or faintly keeled; size large; 

 young specimens striped and spotted dorsally. 



Zamenis Wagler (page 103). 

 BB. Posterior maxillary teeth with grooves; anal plate divided; loreal 

 plate absent; scales smooth. 



Tantilla Baird and Girard (page 106). 



AA. Head with a pit on each side between the eye and nostril; fangs present, 



large, hollow, and erectable; species venomous. . . CROTALIDAE. 



L. Top of head covered with closely set, small scales, excepting the 



large supraocular plate above each eye. 



Crotalus Linnaeus (page 107). 

 LL. Top of the head covered by nine large plates. 



Sistrurus Garman (page no). 



Family Colubridae 



To this family belong the majority of species of snakes. The 

 family as a whole is known as one of harmless snakes. 



Genus THAMNOPHIS Fitzinger 



Thamnophis Fitzinger, Syst. Rept., p. 26, 1843. 



Eutainia Baird and Girard, Cat. N. Am. Reptiles, Pt. I, p. 24, 1853. 



Eutaenia Cope, Proc. Am. Phil. Soc, p. 495, 1886. 



Anal plate entire (we have an exceptional specimen from Meeker, 

 Colo., of Thamnophis elegans, with the anal plate divided); scales in 

 17 to 23 rows, all distinctly keeled excepting those of the first row on 

 each side, which are also usually more or less keeled; superior labials, 

 usually 7 or 8, sometimes 6 or 9; preoculars, 1, sometimes 2, rarely 3; 

 posterior maxillary teeth, especially the last two or three, longer 



