1916] 



Taylor: Beavers of Western North America 



427 



while the porcupine belongs to the section Hystricomorpha. If the 

 above-mentioned resemblances are not due to inheritance from a 

 i common ancestor, and the bulk of evidence 



"~'^'v~"^ would seem to indicate that they are not, they 



Fig. D. 



Lateral view of mandible, to 

 show method of taking 

 measurements. About one- 

 half natural size. 



at the narrowest part of the 

 interorbital constriction. 



Bailey (1905, p. 122) refers 



