340 



than the middle third, though sometimes equaling it; but it is never 

 wider, as it almost invariably is in U. horribilis and U. arctos. The Pu- 

 get Sound specimens have the anterior third the narrowest ; in Alaskan 

 specimens, it reaches its extreme width, while New York and Louisiana 

 examples present the medium phase. 



The skulls of U. cinnamomeus do not seem to be in any way dis*- 

 tinguishable from average skulls of U. americanus, the distinction be- 

 tween them being one of color only and inconstant as characterizing any 

 particular locality or region. 



The upper molar teeth of U. americanus, as shown by the subjoined 

 measurements, differ considerably in size in fully adult specimens. The 

 first molars range in length of crown from 0.40 to 0.52, and in the width of 

 the same from 0.27 to 0.42. The second ranges in length from 0.67 to 0.78 ; 

 the third from 0.94 to 1.22, and in width from 0.51 to 0.67 ! In two speci- 

 mens, with the first 0.44 in length, the third in one has a length of only 

 0.94 and the other 1.07 ! In another, the length of the first molar is 0.41 

 and the third 1.11. In still another, with the length of the first molar 

 0.43, the length of the third is 0.96. In two others, while the length 

 of the first molar is 0.50 in each, the third molar in one has a length of 

 1.22 and in the other 1.15. 



The largest skulls of U. americamis nearly equal in size the smaller 

 skulls of U. arctos liorribilis^ and actually overlap the series from Frank- 

 lin Bay and the measurements given by authors of the true arctos of 

 the Old World. In view of this fact, and of the great range of individual 

 variation in size, cranial and dental characters, and the unreliability of 

 color as a specific character, I too hastily, in former papers,* referred all 

 the American land-bears, including the U. americanus, to the U. arctos, 

 which I am now convinced was a mistake; U. americanus being, I now 

 believe, unquestionably specifically distinct, and the Grizzly subspecifi- 

 cally separable from the U. arctos of the Old World. 



* Bulletin Mus. Comp. Zool., vol. i, pp. 184-192, Oct., 1869 : Bulletin Essex Institute, 

 vol. vi, pp. 46, 54, 59, 63, 1874. 



