UKSUS SPEL^EUS. 89 



If, however, the differences which have been pointed 

 out in the upper jaw and teeth of the Ursus speleeus, as 

 compared with the Ursus maritimus and U.ferox, should he 

 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. speleeus. 



The lower jaw of the Ursus speleeus 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 in a somewhat less 

 degree, from the Ursus ferox, and from the Black Bear of 

 Europe (Ursus Arctos). 



The posterior molar tooth, in the lower jaw, is always 

 broader in proportion to its antero-posterior diameter in the 

 Ursus spelaus 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 

 speleeus ; as, for example, the long and edentulous interval 



ferent de ce que nous trouvons dans fU. Arctos, et surtout dans VU. Arctos ferox 

 de 1'ouest del'Amerique septentrionale." Osttoyraphie des Ours, 4to. 1840, p. 57. 

 * This formation is shown at a, Jiff. 27. 



