651 



Family Ursidee. 



Genus Ursus. 

 Dental formula : i ^ a , c^,p^,m ~=42. 



3979. The skeleton of a young Polar Bear (Ursus maritimus). 



The vertebral formula is: 7 cervical, 15 dorsal, 6 lumbar, 5 sacral: the caudal series is 

 incomplete. In this skeleton there is one more true vertebra than hi that of the Black Bear 

 (No. 4013) or Labiated Bear (No. 4037), but it may be an individual variety*. There is no 

 trace of clavicle in any species of Ursus. 



Mrts. Brookes. 



39SO. The cranium of a very old male Polar Bear (Ursus maritimus}. 



The canines have been broken, the molars worn down, and the sutures obliterated. The 

 socket of the first premolar (pi) still remains on the right side, but those of all the three 

 rudimental premolars (p 1, p 2 &p 3) have been obliterated on the left side. The sagittal 

 crest commences about one inch and a half behind the postorbital processes. 



Hunterian. 



3981. The skull of an old male Polar Bear (Ursw maritimus). 



Most of the sutures are obliterated. The three rudimental premolars (p 1, p 2 & p 3) have 

 been retained with the fourth normally developed one (p 4), on the left side of the upper jaw, 

 but the socket of the second premolar (p 2) has been obliterated on the right side. 



From Hare Island, Baffin's Bay. 



Presented by Dr. Leach, F.L.S. 



3982. The skull of a large old male Polar Bear (Ursus maritimus). 



Almost all the sutures are obliterated. The lower extremities of the occipital condyles are 

 united by a ridge, which, however, is less prominent than in the Ursus ferox. Both paroccipi- 

 tals and mastoids are well developed, but the latter are much the larger processes. The tem- 

 poral ridges, commencing at the postorbital processes, converge at a right angle and meet at 

 about two inches behind the orbits, and form a long and prominent sagittal crest, the upper bor- 

 der of which is straight ; the frontal region is low and flattened : the molar teeth are relatively 

 much smaller than in the Ursus arctos or Ursus ferox : in the interspace between the canines 

 and last premolars are the sockets of two small premolars in both the upper and lower jaws. 



Hunterian. 



* According to M. de Blainville (Osteographie des Carnivores, Ursus, p. 22), the number of dorsal 

 vertebrae in the skeleton of the Polar Bear in the Museum of Comparative Anatomy in the Jardin des 

 Plan tea is only 13, and it has 6 lumbar vertebrae, making one less than the typical number of 'true 

 vertebrae.' 



4o 2 



