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



The zygomatic arches were widest behind, and the arch was somewhat flattened. The 

 malar bone formed a larger proportion of the arch than in Otaria. The antero- 

 posterior diameter of the orbital cavity, from the antorbital process to the ascending 

 process of the malar was in No. 2 T 9 x ths and in No. 1 ^-Jths of the distance from the 

 cranial box to the antorbital process. The orbital process of the malar was pointed, and 

 the zygomatic process of the temporal only reached its base, and did not therefore turn 

 up behind it. 



The nasal bones were separate, and received posteriorly a mesial process of the frontal 

 between them. The anterior border of the mes-ethmoid did not extend quite as far as 

 the anterior border of the nasals. The anterior end of the vomer reached to 22 mm. of 

 the tip of the premaxilla. The horizontal part of the premaxillse was short, so that the 

 anterior nares came close to the anterior end of the skull, and the premaxillse projected so 

 far in front of the superior maxillae that the upper canines were well behind the incisor 

 teeth. The ascending process of the premaxilla formed the lateral boundary of the 

 anterior nares and articulated with a little more than the anterior half of the outer 

 border of the nasal. The superior maxilla articulated with the nasal behind the pre- 

 maxilla, but a small part of the frontal also joined the outer border of the nasal behind 

 the superior maxilla. The maxillo-turbinals did not quite reach the anterior nares, the 

 plane of which sloped obliquely downwards and forwards to the incisive region, well in 

 front of both the antorbital process and the relatively large infraorbital canal. The post- 

 orbital processes were transverse and distinctly larger than the antorbital. As the left 

 process was broken off in each skull the width in this region could not be taken. 



The hard palate was only slightly concave. Its posterior edge was transverse at and 

 on each side of the mesial suture ; it was so far in front of the glenoid fossa as to be in 

 the same transverse plane as the orbital process of the malar bone ; and the interval from 

 the posterior edge to the last molar tooth was only 20 mm. The most anterior part 

 of the palato-maxillary suture was opposite the 4th pair of post-canines, which were 

 distinct, and curved backwards, downwards, and outwards, and the posterior border 

 of the hard palate was 29 mm. iD front of the hamular pterygoids. The palatal plates 

 of the palate bones did not contribute so much to the formation of the hard 

 palate as the corresponding plates of the superior maxillae, the dentary border of 

 which latter bones extended almost as far back as the posterior edge of the hard palate. 

 The palatal surface of each premaxilla was quadrilateral in shape, and each contained a 

 large naso-palatinc canal. The posterior edge of the vomer sloped very obliquely forwards, 

 and was not seen at the posterior nares, which openings were not nearly so far back as 

 in Otaria, and permitted the junction between the pre- and post-sphenoids to be seen. 



Both the crania had alisphenoid canals and mastoid processes. The tympanic bulla 

 was almost flattened and marked by only a low ridge. The occipital condyles were 

 separated by a wide interval in front, and their inner borders anteriorly were almost 



