32 THE VOYAGE OF H.M.S. CHALLENGER. 



they diverged from each other posteriorly so as to admit between them in the middle line 

 an anterior or nasal prolongation of the frontal bone. The anterior border of the mes- 

 ethmoid was vertical, but did not quite reach the anterior nares. The anterior end of 

 the spout-like vomer terminated a little in front of the anterior border of the nasals. 

 The horizontal part of the premaxdla was relatively short, and gave origin to a nasal 

 tubercle»close to the floor of the anterior nares ; in one of the larger skulls the depth of 

 the bone from the anterior nares to the alveolar border was 45 mm., in one of the smaller 

 only 18 mm. The ascending part of the premaxilla mounted upwards and formed the 

 lateral boundary of the nares, and by its upper end articulated with somewhat more than 

 the anterior half of the outer border of the nasal bone. The superior maxilla articulated 

 with the rest of the outer border of the nasal, and completely shut out the frontal from 

 this border. A large, much divided maxillo-turbinal occupied the interval between the 

 mes-ethmoid and the outer wall of the nose, but it did not come quite so far forwards as 

 in the Elephant Seal. The plane of the anterior nares sloped downwards and forwards 

 from the nasal bones to the premaxilla, and the opening was well in front of both the 

 antorbital process and infraorbital foramen. Although the large males possessed massive 

 canines, yet the anterior end of the superior maxillae with their canines did not lie so 

 near to the transverse plane of the incisor teeth as in the Elephant Seal. 



The postorbital processes were transverse in direction, much larger than the ant- 

 orbital in all the crania, but in the two large crania the antorbitals were several times 

 larger than in the smaller skulls. From Table IV. it will be seen that the skulls differed 

 greatly in width in this region, and this difference in relation to their almost equal length 

 was especially marked in the Maldonado and Chincha Island specimens. In the West 

 Falkland adult a strong fibrous band passed from the postorbital process to the zygoma, 

 and completed the orbital ring posteriorly. 



The hard palate had the characteristically elongated form of the genus. In the larger 

 skulls the concavity was much deeper in proportion to the size of the specimens, and the 

 borders of the palate behind the molar teeth converged more closely together than in 

 the smaller crania. The distance from the last molar tooth to the posterior edge of 

 the hard palate was 101 mm. in the large West Falkland Island skull. The greatest 

 palatal width of the larger skulls was either between the canines or the more anterior 

 post-canine teeth, and in the smaller skulls immediately behind the last molar. The 

 premaxilla? were not so distinctly triangular as in the Elephant Seal, and each contained 

 a well-defined naso-palatine foramen. The most anterior part of the palato-maxillary 

 suture was triangular, and either just behind or opposite the last molar tooth. The 

 palatal surface of the palate bone formed nearly one-half of the length of the hard 

 palate, but in one of the larger crania the proportion varied on the two sides owing 

 to these bones not being symmetrical. The dentary border of the superior maxilla, 

 although continued behind the last molar, yet did not nearly reach the length of the 



