TABLE OF CONTENTS. 



Page. 



Table of contexts v 



List of illustrations ix 



Introduction 1 



The taxonomy of the garter-snakes 3 



Present status of the genus 3 



Methods employed 4 



Material examined 7 



Acknowledgments 7 



Genus Thamnophis 8 



Description 8 



Scutellation 8 



Color 10 



Range 12 



Habits and habitat relations 12 



Variation 15 



Variation in scutellation 16 



Variation in number of dorsal scale rows 16 



Variation in number of labial plates 22 



Variation in number of ventral and subcaudal plates, and in prt)por- 



tionate tail-length 31 



Variation in number of preoculars, and in arrangement of lateral spots. 32 



Variation in stripes 33 



Variation in color 37 



The four groups of garter-snakes 39 



The Radix group (megalops, marcianus, radix, and liutlfri i 44 



Megalops 44 



Description 44 



Habits and habitat relations 44 



Range 46 



Variation 47 



Affinities 58 



Marcianus 58 



Description 58 



Habits and habitat relations 59 



Range 5& 



Variation 64 



Affinities : 66 



Radix 70 



Description 70 



Habits and habitat relations 71 



Range j. 76 



Variation 82 



Affinities 86 



V 



