14 MAMMAIiS. 



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



less perfectly digitlgrade. . . . Mttstbud^, 3. 



ii Teeth 40 or 43; body stout; feet completely plantigrade. 



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



molars ; body very large and heavy. . UBSm^, 4. 



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



two true molars ; body moderately stout. 



Procyonid^, 5. 



B. FAMILIES OF UNGULATA. 



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



or 83. Cbrtid.*, 6. 



C. FAMILIES OF CHIROPTERA. 



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



the last joint exserted. . . . YsiSPSRTiLiomBM, 7. 



D. FAMILIES OF INSECTIVORA. 



* No external ear; fore feet greatly enlarged — adapted for 



digging ; limbs very short. . . . TALPiD.ffl!, 8. 



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



SOEICID^, 9. 



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. . . . CAStORrD^, 11. 

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



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



molars f !| GEOMTiDiB, 13. 



aaa. Tail and hind legs excessively elongated, the latter 



adapted for leaping ; molars f ;f • . ZAPODiD.ffl), 18. 

 aaaas.With none of the preceding combinations. 



