URSUS SPELAUS. 89 
Tf, however, the differences which have been pointed 
out in the upper jaw and teeth of the Ursus speleus, as 
compared with the Ursus maritimus and U. ferox, should be 
deemed explicable on the influences of age, sex, and climate, 
no known extent of the operation of these causes can 
account for the differences which are observable in the 
dentition of the lower jaw, and in other characters derivable 
from the skeleton of the U. speleus. 
The lower Jaw of the Ursus speleus differs from that of 
the Ursus maritimus in the greater convexity of the 
inferior contour of the ramus of the jaw, in which 
latter circumstance it differs, though im a somewhat less 
degree, from the Ursus ferow, and from the Black Bear of 
Kurope (Ursus Arectos). 
The posterior molar tooth, in the lower jaw, is always 
broader in proportion to its antero-posterior diameter in the 
Ursus speleus than in the Ursus ferox, and still more so 
than in the Ursus Arctos. The space between the canine 
and the series of the last four molar teeth is usually longer, 
and almost always edentulous and without any trace of the 
sockets of the small deciduous premolars: the first of the 
four persistent grinding teeth has a more complex crown 
than in the Ursus priscus, or in any existing species of Bear : 
besides the principal cusp there are two small tubercles on 
its inner side, and a ridge extending along the outer and 
back part of the base of the crown. 
An entire right half or ramus of the lower Jaw of a Bear, 
from the lacustrine formation near Bacton on the Norfolk 
coast,* presents all these distinctive characters of the Ursus 
speleus ; as, for example, the long and edentulous interval 
férent de ce que nous trouvons dans /’U. Arctos, et surtout dans 1’?U. Arctos ferox 
de louest de l’Amérique septentrionale.”—Osléographie des Ours, 4to. 1840, p. 57. 
* This formation is shown at a, fig. 27. 
y 
