REPTILES 20I 



Key to Genera of Colubridae 



(Several genera appear more than once in this key) 

 ai Some or all of scales on body keeled, 

 bi Anal double. 



Ci Rostral pointed, upturned, and keeled above Heterodon. 



Co Rostral normal. 



di Loreal, preoculars and two internasals present; head scales normal, 

 ei Scale rows 17. 



fi Uniform green above Opheodrys. 



f 2 Not_,uniform green . 



gi Brown stripes Seminatrix. 



g2 Dark with a light dot on each scale Drymobius. 



to Scale rows more than 17. 



fi Scales heavily keeled; 3 postoculars (if 2, scales 



19-23) Natrix. 



{2 Scales weakly keeled; 2 postoculars; scales 25-33 Elaphc. 

 6.1 Some of head scales absent. 



Ci Loreal absent Storeria. 



62 Loreal present. 



fi A single internasal. 



gi Scales 17 Potamophis. 



g2 Scales 19-21. 



hi A preocular Liodytes. 



h' No preocular Farancia. 



f2 Two internasals, no preocular. 



gi 7 Upper labials Abastor. 



g2 6 Upper labials Virginia. 



g3 5 Upper labials Potamophis. 



bo Anal single. 



Ci Scales 29-35; 4 prefrontals Pituophis. 



Co Scales less than 29; 2 prefrontals. 



di Eye in contact with labials; rostral normal. 



ei Upper labials more than 5; striped Thamnophis. 



62 Upper labials 5; not striped Potamophis. 



6.2 Eye cut off from labials by small scales; rostral very 



large and patch-like Phyllorhynchus. 



a2 Scales smooth (not keeled), 

 bi Anal single. 



ci Eye cut off from labials by small scales; rostral very large 



and patch-like Phyllorhynchus. 



Ci Eye in contact with labials; rostral normal. 



di Scale rows on body more numerous in the middle. 



Ci Subcaudal plates mostly single Rhinocheilus. 



ti Subcaudal plates all double. 



fi Belly immaculate; rostral prominent Arizona. 



I2 Belly with some markings; rostral not prominent Lampropeltis. 

 di Scale rows on body same number throughout. 



ei Scales 17 Drymarchon. 



