IO 



Genus Liopeltis. 

 Body slender. One nasal ; one or two preoculars ; loral 

 present. Scales smooth 



Green above, excepting labials, which are yellow; 

 under side, pale yellow L. vernalis. 



Genus Opheodrys. 

 Body very slender ; tail long. One nasal ; one ante- 

 ocular ; loral present. Scales carinated. 



Green above, with the labials yellow; beneath, pale 

 yellow 0. cestivus. 



Genus Bascanion. 

 Body moderately slender. Two nasals; two preoculars; 

 loral present. Scales smooth. 



Uniform black above and below, with the throat 

 white B. constrictor. 



Genus Callopeltis. 

 Body moderately stout. Two nasals ; one preocular; 

 loral present. Scales generally carinated. 



Scales weakly carinated. Black above ; beneath, 

 anteriorly white blotched with gray becoming uni- 

 form slaty gray posteriorly C. obsoletns. 



Genus Heterodon. 

 Body stout. Rostral upturned; oculars numerous; labials 

 not entering orbit. Scales carinated. 



Dark yellow or brown with darker transverse 

 blotches H. platyrhinus. 



Genus Thamnophis. 



Anterior and posterior oculars present. Two nasals; 

 one loral. Scales carinated. Anal plate entire. 



One anterior and three posterior oculars. Brown or 

 black above, with three yellow stripes. Lateral 

 stripe on third and fourth rows of scales. Form very 

 slender T. saurita. 



