1916] Taylor: Beavers of Western North America 441 



In general, the table of comparisons (see table XII, opposite p. 

 440) shows leucodonta to be paler than phaeus. 



Difference in amount of hair is marked. The pelage is lighter 

 weight in leucodonta than it is in either phaeus or canadensis. 



XIII. Measure mexts and Ratios ok Scalded Portions of Tails 

 All measurements in millimeters, and taken in dry skins; see fig. H, p. 431 



Ratio 

 Museum width to 



Subspecies — number Length Width length 



Castor c. leucodonta 12101 237 120 51.0 



Castor c. leucodonta 12111 243 108 44.6 



Castor c. leucodonta 12107 270 124 46.0 



Castor c. canadensis 174525 265 116 43.4 



Castor c. canadensis 174526 260 108 41.3 



Castor c. canadensis 4358 223 92 41.1 



Castor c. phaeus 209 240 130 54.1 



Castor c. phaeus 210 248 132 53.2 



General cranial characters. — Crania compared (being of approx- 

 imately same age) : nos. 12101 £ , 12107 9 , 12111 £ , Mas. Vert. 

 Zool., from Vancouver Island ; nos. 174525 £ . 174526 5 , U. S. Nat. 

 Mus., from New Brunswick; nos. 209 £ , 210 £, Mus. Vert. Zool., 

 from Admiralty Island. 



Leucondota (see tables of measurements, opp. pp. 426 and 438) is 

 separated from canadensis by the following characters: External 

 outline of nasals different, tending to be more parallel in leucodonta 

 than in canadensis, in which there is a dilation in the outline anteri- 

 orly; foramen magnum slightly broader in leucodonta ; hamular 

 processes (see fig. F, p. 430) definitely broader bladed in leucodonta 

 (no. 12107, 4.4 mm.; 12101, 4.6; 12111, 4.8. No. 174525, 3.5; 174526, 

 3.1). 



Distance between most dorsal point on curve of foramen magnum 

 and point of junction of lambdoidal ridge and sagittal crest (inion, 

 see fig. G, p. 431) greater in the eastern subspecies, as shown by the 

 following figures : 



XIV. Measurements, Foramen Magnum to Inion 

 Measurements in millimeters 



Basilar length Distance foramen 



Specimen number of Hensel magnum to inion 



12101 111-9 15- 4 



12111 110.9 18.1 



12107 122.7 18.5 



174525 117.6 20.9 



174526 115.2 19.9 



