CONTENTS. 



P.age. 



Introduction 7 



General habits 8 



Burrows 8 



Food habits 10 



Damage to crops 10 



Winter habits 11 



Breeding habits 11 



Disposition 13 



Pocket gophers as food 13 



Natiu'al enemies 13 



Destruction of pocket gophers 14 



General characters 14 



Cranial characters 16 



Dentition 17 



Sexual variation 17 



Molt 18 



Abnormal pelage conditions. 20 



Albinism 20 



Melanism _ 21 



Variation and distribution 22 



Material examined 30 



Acknowledgments 31 



Genus Thomomys 32 



Generic characters 32 



Group relationships 32 



Heavy rostrum groups 32 



Slender rostrum groups 33 



List of species and subspecies, with type localities 34 



Key to groups of related species 36 



Key to species and subspecies 36 



Description and distribution of species and subspecies 40 



Thomomys hulhivorus group - 40 



Thomomys townsendi group 42 



Thomomys hottx group ^ 45 



Thomomys alpinus group 63 



Thomomys perpallidus group - 68 



Thomomys fulvus group 80 



Thomomys umbrinus group 89 



Thomomys talpoides group : 96 



Thomomys fossor group Ill 



Thomomys douglasi grou-p 116 



Thomomys monticola group 121 



Thomomys fusms group - 126 



Index 133 



3 



