Chapter I: Introduction: 7

PALEONTOLOGICAL HISTORY 10

SKELETON AND DENTITION 12

DISPARITY IN NUMBERS OF MALES AND FEMALES 19

MATERIALS, ACKNOWLEDGMENTS AND METHODS 21

VARIATION 24
Variation with Age 24
Secondary Sexual Variation 26
Individual Variation 28
Seasonal Variation 30
Variation in Coloration and Molt 30
Variations of Taxonomic Worth 44

DISTRIBUTION AND SPECIATION 54

HISTORY OF CLASSIFICATION 69
Chronological List (annotated) of Specific and Subspecific
Names Applied to American Weasels 71

CHECK-LIST OF AMERICAN SPECIES AND SUBSPECIES OF THE GENUS
MUSTELA 81

ARTIFICIAL KEY TO AMERICAN SPECIES OF THE GENUS MUSTELA 83

DIAGNOSIS OF THE GENUS 83

EXPLANATION OF SYSTEMATIC TREATMENT 84

SYSTEMATIC ACCOUNTS OF SPECIES AND SUBSPECIES 87
_Mustela erminea_ 87
_Mustela rixosa_ 168
_Mustela frenata_ 193
_Mustela africana_ 406

EXPLANATION OF CRANIAL MEASUREMENTS 417

TABLE OF CRANIAL MEASUREMENTS 418

LITERATURE CITED 442

INDEX 461

American Weasels

By E. RAYMOND HALL