68 report — 1842. 



on the atmosphere as a physical cause of the inflation of the bony cells, it 

 would be more profitable, if it were possible, to trace the relationship between 

 the different degrees of development which the frontal sinuses may present in 

 different species of Bears, and their peculiar habits and modes of life. We 

 may thus, I think, see the reason why, in the piscivorous species of the Polar 

 ice, the receptacles of air in the bones of the head are least developed, viz. 

 to offer least resistance to its progress through the water when diving after 

 its prey. 



The opposite extreme in the condition of the frontal sinuses of the Ursus 

 spelceus, may have had some corresponding relation to the habits of that gi- 

 gantic extinct species. 



From the great proportional size and more complicated tubercular surface 

 of the posterior molar teeth, especially in the upper jaw, and from the 

 greater complication on the crown of the smallest persistent molar in the 

 lower jaw, one might be led to suppose that the Ursus spelceus fed more on 

 vegetables than the Grisly Bear does. 



If this were the case, one might infer from the slight traces of abrasion in 

 the teeth of full-grown specimens, that the vegetable food, in whatever pro- 

 portion it entered into their diet, was of a soft nature, as berries, or tender 

 twigs or sprouts. The size and strength of the Ursus spelceus would, how- 

 ever, enable it to cope with the large Ruminants and ordinary Pachyderms, 

 its contemporaries in ancient Britain and on the Continent, and to success- 

 fully defend itself against the large Lion or Tiger, whose remains have been 

 found in the same caverns. 



I proceed next to speak of other species of Ursus, of which the fossil re- 

 mains have been found in the caves and superficial deposits in this country. 



A large proportion of a lower jaw, with the incisors, canines, and the entire 

 series of molar teeth on both sides, from Kent's Hole, corresponds with the 

 jaw of the Ursus priscus, Goldfuss. The size is much inferior to that of the 

 Ursus spelceus ; while the worn surface of the teeth proves the animal to have 

 been mature, and probably aged. 



The socket of the first fangless small premolar is immediately behind the 

 canine, and a trace of the socket of a similar premolar is visible near the first 

 double-fanged molar. The interspace containing the simple sockets of the 

 two small premolars is relatively longer than in the Brown Bear or White 

 Bear. The last true molar is relatively smaller than in the Ursus spelceus. 



The Oreston Ursine fossils appear to me to be referable also to the Ursus 

 priscus. 



The most remarkable fossils of the Ursine family which have been found 

 in this country, are those of the Ursus cultridens, or at least of a species closely 

 allied to that from Auvergne and the Val d'Arno ; the singularly compressed 

 and serrated canines of which suggested to Cuvier the specific name above 

 quoted. The evidence of this species, since made the type of a distinct 

 sub-genus under the names of Machairodus and Stenodon, which British 

 localities have afforded, consists of detached canine teeth found in Kent's 

 Hole. These are larger and broader in proportion to their thickness, and 

 have shorter fangs than the Auvergne tooth figured in the ' Osteography ' 

 of M. de Blainville. 



The crown of one of the canines of the Ursus cultridens, from Kent's Hole, 

 measures 2-g- inches ; the fang of a second canine, with the apex of the canine 

 worn down, is 2^ inches in length ; the breadth of the base of the crown is 

 1 inch 2 lines ; its thickness half an inch. 



The oldest fossil referable to the genus Ursus which I have yet seen, is the 

 crown of a molar tooth, found associated with remains of a large species of 



