OCR Text |
Show 336 than in the others. Specimens of U. horribilis, from the same locality, however, differ more among themselves in this respect than the average difference between U. horribilis and U. arctos. The teeth, however, in U. arctos are relatively larger than in U. horribilis, the difference being quite appreciable. The teeth of the Franklin Bay specimens ( 17. richardsoni), on the other hand, are of the same relative size as in the Old World examples of U. arctos. After a careful consideration of the subject, I believe the Barren Ground Bear of Richardson ( U. ricJiardsoni of Mayne Beid) to be not even subspeciflcally distinct from the true U. arctos of the Old World. The Grizzly, from its larger size, widely different geographical distribution, apparently larger claws, slight differences in the dentition and in the form of the frontal region of the skull, may be so regarded ( U. arctm subsp. horribilis), as it can hardly be doubted that it gradually passes into the Barren Ground form'. The subjoined table of detailed measurements of the skulls of U. arctoi liorribilis indicates the wide range of individual variation that may be looked for among skulls from the same locality. These variations not only affect the ratio of width to length, through the greater or less elongation of the facial portions of the skull as compared to the rest, but also all the other proportions are more or less variable, including even the teeth themselves. Thus, two specimens from California, of practically the same length ( 15.60 and 15.40), vary in breadth from 8.10 to 9.05, while two others vary still more, one, with a breadth of 9.20, having a length of only 14.50, while another, with a breadth of 8.50, has a length of 16.001 In these last, the ratio of width to length varies from 0.53 to 0.63. In two California specimens of practically the same length ( 15.60 and 15.75), the length of the last molar varies from 1.43 to L58. In the series of California specimens alone, the length of the last molar varies from 1.35 to 1.66, and the width of the same from 0.67 to 0.80, the widest tooth being, furthermore, not the longest. As already stated, the last upper molar attains its greatest width near the anterior border, bat in several specimens the width of the anterior third is nowhere greater than the width of the tooth at its middle; and the same is also sometimes true in U. richardsoni. |