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Introduction 546
Historical 546
Methods, Materials, and Acknowledgments 547
Evaluation of Characters 548
Characters in which the Subgenera _Eutamias_
and _Neotamias_ Agree, but Differ from the
Genus _Tamias_ 548
Structure of the Malleus 548
Structure of the Baculum 549
Structure of the Hyoid Apparatus 552
Presence or Absence of P3 553
Length of Tail in Relation to Total Length 553
Color Pattern 554
Characters in which the Subgenus _Eutamias_
and the Genus _Tamias_ Agree, but Differ
from the Subgenus _Neotamias_ 554
Shape of the Infraorbital Foramen 554
Width of the Postorbital Process at Base 554
Position of the Supraorbital Notch 554
Degree of Convergence of the Upper Tooth-rows 554
Degree of Constriction of the Interorbital Region 555
Shape of the Pinna 555
Structural Features that are too Weakly Expressed
to be of Taxonomic Use 555
Discussion 555
Genera and Subgenera 557
Genus _Eutamias_ Trouessart 557
Subgenus _Eutamias_ Trouessart 558
Subgenus _Neotamias_ Howell 558
Genus _Tamias_ Illiger 559
Discussion 559
Conclusions 560
Literature Cited 561