Vol. XXVI, pp. 191-194 October 23, 1913 



PROCEEDINGS 



OF THE 



BIOLOGICAL SOCIETY OF WASHINGTON 



TWO NEW SUBSPECIES OF NORTH AMERICAN 



BEAVERS. 



BY VERNON BAILEY. 



In my report on the mammals of Texas* in 1905 I referred 

 the beavers of the Rio Grande and Pecos rivers to Castor cana- 

 densis frondator Mearns. Since that time specimens have been 

 collected at additional localities along the Rio Grande and its 

 tributaries, and in working over the material in the Biological 

 Survey collection from New Mexico I find that the beavers of 

 the Rio Grande drainage differ so markedly and constantly 

 from those of the Colorado drainage that it becomes necessary 

 to provide a name for them. Other specimens from the Upper 

 Peninsula of Michigan brought into the comparison of material 

 also prove to be so different from typical canadensis that a 

 subspecific name is required for them. These two forms 

 show what appear to be the opposite extremes of pale desert 

 coloration in those from the Rio Grande region and dark, rich 

 coloration of those from the densely shaded forest area of 

 northern Michigan. The cranial characters are also well 

 marked. 



Castor canadensis mexicanus subsp. nov. 



RIO GRANDE BEAVER. 



Type from Ruidoso Creek, six miles below Ruidoso. New Mexico, $ 

 adult, No. 96,522, U. S. Nat. Mus., Biol. Survey Coll., collected by C. 

 Barber, Sept. 29, 1899. Collector's number, 83 (Biol. Surv. X catalogue 

 No. 1991). 



General characters. — Size medium, colors dull and pale with very little 

 chestnut at any season. Skull relatively short, wide and high. 

 • North American Fauna No. 25, Biological Survey of Texas, p. 124, 1905. 

 ■19— Proc. Biol. Soc. Wash., Vol. XXVI, 1913. (191) 



