QUATEENAET FAUNA OP GIBEALTAE. 



69 



The evidence, therefore, as to species afforded by the dentition of the Gibraltar Bear, 

 is not very satisfactory, and leaves it doubtful whether it should be referred to U.fossilis 

 or to a large form of U. arctos. 



Another specimen in which we may seek for further evidence is the axis vertebra, 

 which seems to present some distinctive characters from that of TJ.ferox; but these 

 are perhaps not very marked, nor probably of much intrinsic importance. And it 

 must be remembered that the Gibraltar bone is of a young animal, and that with which 

 it was compared of fully mature age. The comparative dimensions of these bones are 

 given in the following table. 



Comparative Dimensions of Axis of Ursus ferox and JJ. , Gibraltar. 



From these figures it will be seen that the main differences as regards dimensions 

 are in the greater width across the anterior articular processes, which would indicate 

 of course a longer atlas and skull, and probably, therefore, a larger animal, which is 

 quite in accordance with the comparative dimensions of the teeth in the two cases. 

 The neui-al canal also is larger in the Gibraltar bone, which is an indication in the 

 same direction, whilst, on the other hand, the total length is slightly less, and that 

 of the spine considerably so — both of which differences may reasonably be assigned 

 to the different ages of the individuals. 



In other respects it is to be observed that in the axis of U. ferox the posterior 

 articular facets are larger and rounder, the transverse processes much larger, the neural 

 laminse thicker, and the odontoid process smaller — all of which differences may also 

 be fairly referred to age and stature. 



The spine in JJ. ferox is produced backwards some way behind the level of the 

 posterior articular processes, whilst in the Gibraltar bone it is on a level with them ; 

 and in the former it is much hollowed posteriorly : but these characters may also 

 perhaps be referred to difference of age. 



1 have also compared the axis with that of U. arctos (var. isabellinns '). The latter 

 is of about the same general size, but differs from the former in several particulars, 

 some of which, but not all, can also be regarded as due to age. 



' I may mention that in this specimen of U. isabelUnus in the British Museum there are six sacral vertebrse. 



VOL. X. — PAKT II. No. 3. — August 1st, 1877. L 



