442 



University of California Publications in Zoology [Vol.12 



C. c. Icucodonta is separated from C. c. phaeus by the following 

 characters: Nasals less tapering posteriorly and shorter in Icuco- 

 donta; interorbital constriction broader; foramen magnum nar- 

 rower (exception, phaeus no. 210 has a narrower foramen magnum 

 than leucodonta no. 12107) ; maxillary tooth-row shorter in Icuco- 

 donta; ratio of maxillary tooth-row to basilar length less; palate 

 anteriorly (see fig. I) broader (no. 12107, 6.9 mm.; 12101, 6.9; 



Fig. I. Ventral aspect of palate, to show 

 method o£ taking measurements. 

 Shorter measurement is "palate 

 anteriorly". Longer dimension is 

 that to show the tooth-flare. Ap- 

 proximately one-half natural size. 



12111, 6.8. No. 209, 5.6 mm.; 210, 5.1) ; blade of hamulars (see fig. 

 P, p. 430) slightly broader (no. 12107, 4.4 mm.; 12101, 4.6; 12111, 

 4.8. No. 209, 4.1; 210, 4.1). 



CASTOR CANADENSIS PACIFICUS RHOADS, FROM THE MAINLAND OF 

 BRITISH COLUMBIA AND WASHINGTON 



Eleven specimens, all from the collections contained in the 

 U. S. National Museum: Puget Sound, 1 (no. 3936, jaws only); 

 Skagit Kiver [Washington], 1 (no. 3672 1 , skull only) ; Lake Cush- 

 man, Mason County, Washington, 8 (nos. 71276, 71812, 71814, 

 78395, 87628, 87629, skulls only, and nos. 71830, 71833, skins only, 

 Biol. Surv. coll., in U. S. Nat. Mus.) ; Keechelus Lake, Washington, 

 1 (no. 126190, Biol. Surv. coll.) ; Fisher, Five River Valley, Ore- 

 gon, 2 (nos. 136605, 136606, skulls only, Biol. Surv. coll.). 



Comparison With Castor canadensis leucodonta Gray, from Vancouver 

 Island, and With Certain Other Species or Beavers 



General external characters. — Material representative of external 

 characters is limited. One young topotype skin of Castor cana- 

 densis pacificus Rhoads, from Lake Keechelus, Washington, is at 

 hand. According to the label it was probably taken in February, 

 1903. No example of Castor canadensis leucodonta strictly corre- 

 sponding in age and season with this topotype of pacificus is at 



i This skull was specified by Allen (1877, p. 441) as from Europe, and was 

 commented upon as presenting an exceptional character. 



