POSITION IN ANIMAL KINGDOM. 45 



him for a long career of life upon the earth, trans- 

 mitted through the species. It is not imjDrobable that 

 his first appearance antedates the present configura- 

 tion of the continents. Of the mastodon but one 

 species, I believe, has been found in America, while 

 several have been discovered in Europe and Asia, 

 neither of which is identical with the American spe- 

 cies. How the beaver, adopting the conclusion of but 

 a single species, propagated himself from one con- 

 tinent to the other, may be wholly unexplainable; 

 but it does not aifect the question whether the two 

 beavers are of the same, or of different species. Of 

 all the mammals without the Arctic Circle in Europe 

 and America, with the exception of man, the beavers 

 of the two continents are probably the only individ- 

 uals whose specific identity can be established by 

 anatomical comparisons. 



The second chapter and Appendix A, as has else- 

 where heen stated, are from the pen of Dr. W. W. Ely, 

 whose able and thorough exposition of the anatomical 

 structure of the American beaver will command the 

 attention of the comparative anatomist, and prove in- 

 structive to the general reader. The comparison of 

 the skulls, referred to on the preceding page, was made 

 by him. 



