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



widest part of the zygomatic arch was at its hinder end, and the arch diminished in 

 width when traced from behind forwards ; in Weddell's Seal the width of the arch was a 

 little greater at its mid-point than posteriorly. In Stenorhynchus the distance from the 

 antorbital process to the most anterior surface of the cranial box as compared with the 

 distance from the antorbital process to the orbital process of the molar was as 9 to 7 ; in 

 Weddell's Seal the former diameter very slightly exceeded the latter. In both specimens 

 of Stenovhynchus the total length of the skull both absolutely and relatively was greater 

 than the breadth as compared with the same dimensions in Weddell's Seal. The skull 

 was capacious in the parietal region, and comparatively flattened in all the crania, and 

 became greatly constricted in the frontal region ; this constriction was relatively longer 

 in Stenorhynchus than in Weddell's Seal. In Leptonychotes the antero-inferior angle 

 of the parietal articulated with the alisphenoid ; in one Stenorhynchus leptonyx they were 

 separated by an epipteric bone ; in the other they directly articulated. 



In all the crania the nasal bones were elongated and ankylosed together posteriorly 

 and mesially. More than one-half of the length was received between the two divisions 

 of the frontal, where they formed a triangular area, with the apex backwards, whilst the 

 anterior part, lodged between the two superior maxillre, was quadrilateral in form. The 

 anterior edge of the mes-ethmoid was situated far back in the nasal chamber, and the 

 spout-like vomer, which contained the septal cartilage, sloped downwards and forwards 

 to the anterior nares. The ascending part of each premaxilla entered into the lateral 

 boundary of the anterior nares, but in Stenorhynchus leptonyx it did not quite reach the 

 nasal bone, whilst in Weddell's Seal it partially articulated with the anterior end of the 

 outer edge of the nasal. The lateral boundaries of the anterior nares sloped obliquely 

 downwards and forwards, so as to bring the floor of the opening close to the anterior end 

 of the rostrum. The interval between the vomer and the side wall of the nose was 

 occupied by a much subdivided maxillo-turbinal. In Stenorhynchus the antorbital process, 

 though small, was distinctly marked, but in Weddell's Seal it was only a faint tubercle ; 

 in the former there was an indication of a postorbital process, which was not visible 

 in Weddell's Seal. The antorbital process and infraorbital foramen in all these skulls 

 were in almost the same transverse plane, and considerably behind the opening of the 

 anterior nares. The ascending process of the superior maxilla was not received between 

 the diverging frontals. 



In all the specimens the hard palate was widest opposite the last molar, and its 

 concavity was very slight. In Stenorhynchus it extended for 40 mm. from the last molar 

 to the palato-pterygoid suture, and in Weddell's Seal for 36 mm., and its border was not 

 raised above the general plane of the palate. The palatal surface of each premaxilla 

 was triangular and the naso-palatine canal was large enough to admit a stilet. The 

 palato-maxillary suture was transverse near the middle line and opposite the last molars, 

 but then sloped backwards and outwards and terminated immediately behind the malar 



