70 ME. G. BUSK ON THE AJVCIENT OE 



1. The spine, which is of the same length, is 1""3 instead of 1"'0, and much more 

 rounded at hoth ends on the upper edge, and much deeper in front (exactly the reverse 

 of U. spelcBUs). Bnt viewed from above it is thinner and much more constricted 

 above the posterior articulating processes. It is also deeply hollowed behind (as in 

 U.ferox). 



2. The body is much narrower in the middle. 



3. The anterior articular processes are smaller and more rounded or convex. 



4. The odontoid process is smaller. 



5. But the most remarkable difference is in the size of the neural canal, which in 

 U. isabellinus is little more than half the greatest diameter of that in the Qibraltar 

 bone. 



6. The form of the posterior surface of the centrum is quite different ; but as the 

 epiphysis is wanting in the Gibraltar specimen, the difference may perhaps be thus in 

 some measure accounted for. The other, as I have observed, can hardly be assigned to 

 age, nor, as it would seem, to the circumstance that the Isabelline Bear was of smaller 

 size than the Gibraltar one. 



Hence, again, then, we are brought to the conclusion that the Gibraltar Bear ap- 

 proached more nearly to U.fossilis or U.ferox than to U. arctos (var. isabellinus). 



As regards the metacarpals, I need only remark that, having carefully compared 

 them with those of U. ferox, of which a good specimen has lately been acquired by 

 the Eoyal College of Surgeons, I can perceive scarcely any difference worthy of note 

 between them. So far as dimensions are concerned, this will be obvious from the 

 accompanying Table (see Appendix, opposite). 



It will be seen, from this Table, that the Gibraltar metacarpals must have belonged 

 to four individuals, and that the largest of these most nearly coincides with the speci- 

 men of U.ferox in the College Museum, which, it is to be remarked, is of small size for 

 that species, and, to judge from the wear of the teeth, rather old. 



In the ffih metacarpal of U.ferox the crescentic tuberosity on the outer side of the 

 head is more pronounced, whilst in the Gibraltar bone it is wider just above the lower 

 capitulum. But the muscular impression i, or tuberosity, on the outer side below is 

 more pronounced in U. ferox. The perimetral index is slightly greater in the 

 Gibraltar bone ; and its shaft very slightly more compressed. 



In the second metacarpal, of which there are two specimens in the Gibraltar col- 

 lection, one considerably smaller than the other, though quite mature, rather more 

 difference is perceptible. In the first place, the proximal end is more produced be- 

 hind than in U.ferox, and the shaft in the smaller specimen very much more com- 

 pressed ; but in the larger of the two this compression is not observable. The distal 

 articular head in both is smaller, and less rounded than in U. ferox. 



' Por insertion of the peronceus brevis ? 



