420 



KANSAS UNIVERSITY SCIENCE BULLETIN. 



third and fourth largest. Inferior labials nine or ten. No su- 

 perior labials enter the orbit. Dorsal rows of scales twenty- 

 three, from nineteen to twenty-one posteriorly. Outer row of 

 scales smooth, as wide as long, second row faintly keeled ; all 

 other dorsal scales strongly keeled. Two nasal plates ; nostril 

 in anterior plate. A deep pit between eye and nostril. Anal 

 plate undivided. Urosteges in some specimens entire ; in others 

 the posterior divided, anterior entire. Antorbitals three. Post- 

 orbitals four to five. Tail short. Urosteges 30-50. Gastro- 

 steges 145-155. 



Fig. 36. 

 Ancistrodon contortrix B. and G. 



Fig. 36(1. 

 ADcistrodon contortrix B. and G. 



