653 



appendages. The mastoid is occupied by a close diploe, which receives no air-cells from the 

 tympanic cavity. In the middle section may be seen the oblique termination of the meatus 

 auditorius within the tympanic cavity. The anterior section shows the triangular constriction 

 which separates the prosencephalic from the rhinencephalic chamber, the latter of which is 

 laid open, together with the olfactory chambers, by an extensive fracture of the upper part of 

 the skull. The lateral walls of the cranium are extremely thin where they give attachment 

 to the temporal muscles. 



In all the foregoing specimens of the Urtus maritimus the median prepalatine foramen is 

 well marked, but is largest in No. 3980. The cranial peculiarities of the Ursu-s maritimus 

 are constant throughout this series of skulls, and give confidence in those that characterize 

 the other species of Bear. The differences which result from age are well seen in the compa- 

 rison of the old skulls with that of the young Polar Bear belonging to the skeleton No. 3979. 

 But in this, as in the other skulls, may be seen the comparatively straight contour of the upper 

 surface, the extension of the long nasal bones behind the extremities of the nasal processes of 

 the maxillaries, and the narrowness and depth of the posterior palatine fissure. 



Hunterian. 



The following, to No. 40 1 1 inclusive, are parts of the same skeleton of the Polar Bear 

 (Ursu* maritimus). 



Hunterian. 



3989. The lower jaw. 3990. The atlas. 



3991. The dentata. 3992. The five other cervical vertebrae. 



3993. Four dorsal vertebrae. 3994. Six lumbar vertebrae. 



3995. The pelvis. 3996. The right scapula. 



3997. The right humerus. 3998. The right radius. 



3999. The right scapho-lunar bone of the carpus. 



4000. The left scapho-lunar bone. 4001. The right femur. 

 4002. The right tibia. 4003. The right fibula. 

 4004. The right patella. 4005. The right astragalus. 

 4006. The left astragalus. 4007. The right calcaneum. 



