14 MAMMALS. 



:): Teeth less. than 40; body rather slender; feet often more or 

 less perfectly digitigrade. . . . Mustelid^, 3. 



Xt Teeth 40 or 42; body stout; feet completely plantigrade. 



«. Tail rudimentary; teeth 42; lower j' aw with three true 

 molars ; body very large and hea^y. . Uksid^, 4. 



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

 two true molars ; body moderately stout. 



PllOCYONID^, 5. 



B. FAMILIES OF UNGULATA. 



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



or 32. ' Cervid^e, 6. 



C. FAMILIES OF CHIROPTERA. 



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



the last joint exserted. . . *. Vespertilionid^, 7. 



D. FAMILIES OF INSECTIVORA. 



* Ko external ear; fore feet greatly enlarged — adapted for 



digging; limbs very short. . . . Talpid^, 8, 



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



SORICID.<E, 9. 



E. FAMILIES OF RODENTIA. 



* Incisors | ; 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^, 11. 



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

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

 molars |'| GEOivryiD^, 12. 



aaa. Tail and hind legs excessively elongated, the latter 



adapted for leaping ; molars f^f- . Z.\podid^, 13. 



aaaa. With none of the preceding combinations. 



