192 BULLETIN OF THE 



to the same species by authors who separate them into numerous species, 

 lessens the importance of distinctions based on them as separating the 

 bears of America from those of the Old World. 



The claws arc well known to vary in length at localities not very remote, 

 in the Old World and in the New. Although the differences between 

 specimens of U. horrib'dis, which seem to have them ordinarily the most 

 developed, and others of U. arclos from Western Europe, is very great, 

 they do not appear to have the importance as specific characters assigned 

 them by Prince Maximilian and Dr. Mayer. 



Finally, in weighing the evidence in reference to the number of species of 

 North American bears and their relationship to those of the Old World, it is 

 evident that the comparatively small number of specimens thus far examined, 

 either from a single region or in altogether, and the vast areas from which 

 no specimens have been received, should be carefully considered as showing 

 how few the data are on which any opinion must be based. The incon- 

 stancy of character presented by those from the same locality, especially in 

 the breadth and other proportions of the skull, in the shape and relative 

 size of the molar teeth, in color, and in size, should also be duly considered, 

 as well as the fact that however wide the differences between specimens 

 from distant localities are, those from intermediate ones are generally of an 

 intermediate character. In some districts bears find an abundant supply 

 of animal food, while in others they are more or less restricted to a vegetable 

 diet, and that these differences must give rise to modifications in the teeth 

 and bones of the skull is to be expected. From the wide geographical 

 range of even the different restricted so-called species, their representa- 

 tives are subjected to widely different climatic and other modifying influ- 

 ences. In America, the coincidence of the greatest number of individuals 

 with the maximum development in size seen in the region occupied by the 

 typical U. horribilis, as in California, and the gradual transition in the east- 

 erly portions of the Rocky Mountain district to aberrant forms of this type, 

 some of which indisputably approach quite near the common style of U. 

 "americanus" of the eastern portions of the United States, and at the 

 extreme north of the continent to the U. arctos of the Old World, espe- 

 cially to the Russian type of that animal, are facts which render the 

 separation of the bears of these several regions into well-defined species 

 quite improbable, if not impossible. I hence see no alternative but to 

 consider with Blainville, Middendorff, and Murry, all the bears of the 

 Northern Hemisphere, excepting Ursus maritimus, as forming but a 

 single species. Here, as in other similar cases already considered in 

 this paper, if the opposite view be adopted, it appears inevitable that still 

 other species than those authors have already recognized must be allowed, 

 with numerous " sub-species," or " varieties" and "sub-varieties" of each, 

 Vr to dispose of the constantly occurring ' ms. 



