14 MAMMALS. 



\ Teeth less than 40 ; body rather slender ; feet often more or 

 less perfectly digitigrade. . . . MUSTELID^, 3. 

 \\ Teeth 40 or 42; body stout; feet completely plantigrade, 

 a. Tail rudimentary; teeth 42; lower jaw with three true 

 molars ; body very large and heavy. . URSID.E, 4. 

 CM. Tail well developed; teeth 40; lower jaw slender, with 

 two true molars ; body moderately stout. 



PROCYONIIXE, 5. 



B. FAMILIES OF UNGULATA. 



* Toes paired (artiodactylous) ; horns solid, deciduous ; teeth 34 



or 32. CEKVIILE, 6. 



C. FAMILIES OF CHIROPTERA. 



* Snout not appendaged ; tail inclosed in the membrane, or only 



the last joint exserted. . . . VESPERTILIONID^B, 7. 



D. FAMILIES OF INSECTIVORA. 



* No external ear; fore feet greatly enlarged adapted for 

 digging ; limbs very short. . . . TALPIDJS, 8. 

 ** An external ear ; feet normal ; hind feet usually longest. 



E. FAMILIES OF RODENTIA. 



* Incisors f ; tail well developed. 

 f Hair forming a fur, without spines. 



a. Tail broad, flat and scaly; feet webbed; molars f'f ; 



body stout and heavy. . . . CASTORID^E, 11. 



aa. Limbs very short, about equal ; fore claws much enlarged ; 



large external cheek pouches ; body thick-set and heavy ; 



molars f !|. ..... GEOMYHXE, 12. 



aaa. Tail and hind legs excessively elongated, the latter 

 adapted for leaping ; molars f !f . ZAPODIIXE, 13. 

 aaaa. With none of the preceding combinations. 



