MUSEUM OF COMPARATIVE ZOOLOGY. 187 



species indicate very considerable differences in the proportion of breadth 

 to length in the entire skull, and in the relative length and slenderness of 

 the muzzle. In consequence of such variations Dr. Gray and Professor 

 Baird arrive at widely different conclusions in reference to the relationship 

 of the U. cinereus Gray ( U. horribilis Baird) to the U. americanus. 



There is a strong tendency among naturalists to consider the Old World 

 bears as all distinct from those of North America, and to recognize at least 

 two species among the latter, — the grizzly bear (Ursus horribilis) of the 

 West, and the continentally dispersed black and brown bears (U. ameri- 

 canus). Professor Baird, in his Mammals of North America, gives the 

 probable number as five, four of which he seems to consider well founded, 

 and thinks that there may be two others. But each of the recognized 

 species presents so many varieties, which to a greater or less extent inter- 

 grade, that well-marked lines of distinction cannot at present be drawn. 

 This has led a recent writer to observe, and it seems to me very justly, 

 " If the same consolidation of species which some authors practise in plants 

 was carried out in animals, we should have but one species [of bear] for 

 the whole northern hemisphere." * 



The present indications are that the U. horribilis is hardly so distinct 

 from the common U. americanus as has been currently supposed ; f it also 

 presents close affinities in many respects with the U. arctos of Europe. 

 Towards the north it shades into what is called the Barren Ground bear, 

 which latter has been repeatedly referred, with more or less positiveness, 

 by different authors to the U. arctos rather than to U. americanus or U. 

 horribilis. Middendorff found the bears of Northeastern Asia equalling 

 in size and generally resembling in other characters the U. horribilis (ferox 

 of authors) of the Western Coast of America. The U. americanus also pre- 

 sents numerous variations in color and in other points quite parallel with 

 similar variations in the European U. arclos.% Specimens often occur on 

 the one continent that are strikingly like others from the other. Midden- 

 dorff expressly states that the differences between U. arctos and U. ferox 

 (horribilis) are not greater than occur between different specimens of U. 

 arctos. Dr. Gray admits that it is only a knowledge of the locality that in 

 some cases enables him to separate them. 



* Andrew Murry, Geog. Distr. of Mammals, p. 119. 



t See Professor Baird's N. Am. Mam., pp. 219-228. 



\ I learn from Mr. W. H. Dall, who has recently returned from a three years' explo- 

 ration of Alaska, bringing with him important information relative to the natural 

 history, geography, etc., of that country, that three kinds of bears are distinguished 

 there; the larger and the more common being the grizzly, the second the so-called Bar- 

 ren Ground bear, while the third and smallest is a black bear ; showing that there 

 is found the usual variety, in point of size and color, seen on the Pacific Coast farther 

 south. 



