1916] Taylor: Beavers of Western North America 451 



Ventral view crania of Castor canadensis leucodonta and Castor 

 subauratus subauratus. Note the different breadth of rostrum; 

 the difference in squareness anteriorly of the zygomata; the 

 difference in hamulars and median process in the interpterygoid 

 fossa; in the mastoids, the paroccipitals, the external auditory 

 meatus, and the position of the occipital condyles. Approxi- 

 mately two-thirds natural size. 



Castor canadensis leucodonta, no. 12107, $, Mus. Vert. Zool.; 

 Alberni, Vancouver Island, British Columbia. 



Castor subauratus subauratus, no. 12654, 9, Mus. Vert. Zool.; 

 Grayson, San Joaquin River, Stanislaus County, California. 



