1916] Taylor: Beavers of Western North America 461 



ships of beavers, some of these being: (1) the relation of the beaver 

 of North America to that of Europe and Asia, and (2) the interrela- 

 tions of the North American forms. Under the second head arises 

 the question whether groupings of the North American forms are 

 possible, and since groupings are possible, further problems arise as 

 to their interrelationships, their ancestry, and the causes and condi- 

 tions in their differentiation. 



The relationships of the American and Eurasian beavers have 

 been more or less fully discussed by the following authors : Geo. 

 Cuvier (1817, tome 1, p. 191, not seen; and 1825, tome 5, p. 57, not 

 seen) ; Fred. Cuvier (1825, liv. 51, not seen) ; Brandt and Ratzeburg 

 (1S27, pp. 12-30); Brandt (1855, pp. 43-66); Morgan (1868, pp. 

 42-45); Ely {in Morgan, 1868, pp. 288-306); and Allen (1877, pp. 

 437-445). While sufficient material to justify a review of this point 

 has not been available, the present writer has been able to compare 

 three skulls of Castor fiber from the Elbe River, Germany, with the 

 American beavers, and believes that the evidence indicates that they 

 are specifically distinct. 



Several points of possible significance arise in connection with 

 the problem of the interrelationships of the North American beavers. 

 Material illustrative of two species of Nearctic beavers, as well as 

 of all their subspecies but two (Castor canadi usis carolinensis Rhoads 

 and Castor canadensis mexicanus Bailey), has been available in this 

 study. Even a cursory examination of this material shows that all 

 those beavers listed under canadensis, namely subspecies canadi axis, 

 michiganensis, belugae, leucodonta, pacificus, frondator and texensis, 

 fall into one group, while those listed under subauratus, namely 

 subspecies subauratus and shush usis, fall into another. Within these 

 groups the subspecies appear to be closely related, their differentia- 

 tion apparently having progressed to a slight extent only. From 

 their geographical situation and from a consideration of such of their 

 characters as may be worked out from the literature, species caecator 

 Bangs and subspecies mexicanus Bailey and carolinensis Rhoads 

 should be referred to the canadensis group. 



The members of the canadensis group are, on the basis of available 

 material, unequally related. For example, Castor canadensis phaeus, 

 from Admiralty Island, Alaska, is less closely related to Castor c. 

 canadensis of eastern Canada than is Castor c. belugae of the opposing 

 mainland. Phaeus is more sharply marked off from the other sub- 

 species of canadensis than are Castor c. frondator or belugae. Phaeus 



