8 THE VOYAGE OF H.M.S. CHALLENGE!!. 



the alveoli, and where in the living animal they would have been embraced by the gum. 

 Also in these older crania the entrance into the pulp cavity was obliterated, excepting in 

 the canines, but in the younger skulls the communication with the pulp cavity at the tip 

 of the fang was freely open in all the teeth. In both of the large males the canines were 

 not only worn down somewhat at the apex, but the lateral aspects, where the upper and 

 lower canines had rubbed against each other, were much flattened. In the Kerguelen 

 Island male (e) the teeth showed very slight signs of wear, so that this animal was far 

 from being adult, 



When the skulls of the females were placed side by side with that of either of the 

 large males, other differences than that of relative size were observed. In the female 

 skull the summit from the occipital crest to the fronto-nasal suture was almost flat, 

 but sloped downwards and forwards on the nasal bones ; the occipital crests were only 

 faintly indicated ; the skull possessed great width in the occipital, parietal, and temporal 

 regions, and then suddenly narrowed in the frontal and interorbital regions. The 

 temporo-zygomatic fossa was capacious and continuous with the orbit, and the zygomatic 

 arch was massive and bulged outwards. In both the large males the temporo-zygomatic 

 fossse and arches were like those in the female, but on a larger scale. The summit of the 

 skull was not flat, but concavo-convex from behind forwards, the posterior concavity being 

 due to the elevation of the occipital crests and posterior border of the parietal bones. 

 The frontal bones were also somewhat depressed below the plane of the two parietals, 

 between the anterior borders of which they were received, but further forwards the 

 frontals were raised into a slight convexity in the interorbital region, and at their 

 anterior ends subsided into a hollow corresponding to the fronto-nasal suture. In the 

 Kerguelen Island young male (e) the occipital crests were much lower than in the other 

 males, and the summit of the cranium was less removed from the flattened form of the 

 skull seen in the female, and this flattening of the vertex was a character in all the young 

 skulls, both male and female. The frontal region in all the crania was constricted as 

 compared with the great breadth of the occipital, parietal, and temporal regions ; but in 

 the males the frontal width in front was proportionally more than in the female, owing 

 to the greater width of the anterior nares in the former sex. In the younger crania the 

 interfrontal width was not so constricted posteriorly as in the adult skulls. The 

 greatest width of the skull at the zygomata was at a point about midway between the 

 two ends of the arch. 



The relative size of the orbits and temporo-zygomatic fossa was studied by com- 

 paring the diameter, measured from the anterior surface of the cranial box at or near 

 the fronto-parietal suture to the tip of the antorbital process, with the orbital diameter 

 from the tip of that process to the apex of the ascending or orbital process of the malar. 

 In the two older males the orbital diameter, as measured between the above two points, 

 was about two-thirds that of the entire distance ; in the younger male (e) the orbital 



