VI 
Contents 
PAGE 
Suborder Simplicidentata .... 56 
Family Erethizontidae • . • • 57 
Family Zapodidas . . . . .61 
Family Heteromyidae .... 64 
Subfamily Heteromyinae . . . . 65 
Subfamily Dipodomyinae .... 65 
Family Geomyidae . . . . -77 
Family Muridae . . . . .91 
Key of Subfamilies and Genera of Muridae 92 
Subfamily Microtinae .... 93 
Subfamily Neotominae . . . .107 
Subfamily Cricetinae . . . .121 
Subfamily Murinae . . . . .137 
Family Castoridae . . . . .140 
Family Sciuridae . . . . -144 
Key of the Genera of Sciuridae. . . -144 
Order Garni vora 187 
Key of the Families of Carnivora . .188 
Family Mustelidae 188 
Key of the Subfamilies and Genera of 
Mustelidae 188 
Subfamily Lutrinae . . . . .189 
Subfamily Mustelinae . . . .192 
Subfamily MeHns 205 
