22 Proceedings of the Royal Physical Society. 



8J inches, that of the summit was only 5J inches. The 

 anterior surface was also flattened, roughly tuberculated, and 

 sloped downwards and forwards so as to form an angle of 

 58° with the horizontal plane. The right crest was some- 

 what bigger than the left, and projected both a little further 

 forward and distinctly further back, so as to approach nearer 

 to the ascending part of the premaxilla. The greatest 

 breadth between the outer borders of the two maxillary 

 crests was 1 foot 5 inches. 



From a comparison of the relative size of the maxillary 

 crests and their intermediate interval in the young and aged 

 male skulls, it is evident that the difference between them is 

 mainly due to the growth of each crest inwards towards the 

 mesial plane, which occasions great narrowing of the inter- 

 mediate interval ; and at the same time the vertical diameter 

 of these crests increases, so that they form the summit of the 

 skull and head. 



On the left side of the head the interval between the 

 posterior border of the maxillary crest and the front of the 

 ascending part of the premaxilla was a little greater than on 

 the right side, and in both the young and aged skulls 

 measured 5 inches. The anterior nares were unsymmetrical, 

 the right nasal and premaxilla being broader, and projecting 

 more forward than the left in both skulls. In the young 

 male the posterior wall of the nose was almost vertical ; in 

 the aged animal it was directed obliquely backwards, so 

 that on looking vertically downwards on the anterior nares 

 they were quite open in the young animal, but almost entirely 

 overlapped by the nasals and ascending parts of the pre- 

 maxillse in the aged skull. In the aged skull also the occi- 

 pital squama sloped upwards and forwards from the foramen 

 magnum ; in the young male it was nearly vertical. 



The bones of the aged male skull were dense, hard, and, 

 where the surface was not abraded by rubbing on the beach, 

 almost porcellaneous in their character. Although portions 

 of this skull were lost, it weighed 308 lbs. ; whilst the 

 younger male, also without a lower jaw, weighed only 37 

 lbs. The old skull, therefore, exceeds by 271 lbs. the weight 

 of that of the young animal, and it is probable that this great 



