REPORT ON THE SEALS. 31 



on its summit antero-posteriorly ; also from each parietal, where it formed the anterior 

 wall of the cranial box, a strong tubercle projected forwards. In the two smaller adult skulls 

 the sagittal and occipital crests were very feeble, and the interfrontal was scarcely marked, 

 and although the frontal bone at the anterior wall of the cranial box bulged forwards, it 

 was not elevated into a tubercular process. 



In the young Falkland Island skull, the crests were undeveloped, the summit of the 

 cranium was smooth and the frontal region was only slightly constricted behind the 

 postorbital processes, and its absolute width was about twice as great as the large male 

 crania. The length of the brain-cavity, measured from the basion to the optic foramen, 

 is given in Table IV., so that its proportional length to that of the entire cranium may be 

 estimated, and in the young skull the antero-posterior diameter of the cranial box was more 

 than one-half that of the entire skull, so that the more anterior part of the skull grows 

 in its progress to adult life at a much greater rate proportionally than the brain-cavity. 



Qq -I 1 



The dentition in all the specimens was as follows : — incisors ^tj » canines y^ ' post- 



c & 



canines -p — ? = 36. The individual teeth in the adults possessed the characters which have 



so frequently been described in Otaria, so that I need not dwell upon them. 



The teeth in the young male were so much smaller than the adult that they were 

 apparently the milk series. In the upper jaw only two incisors on each side, each with 

 an anterior and a posterior cusp, bad cut the gum ; in. 3 being still concealed. Very 

 small canines had erupted, and the points of the 1st and 2nd post-canines could be seen. 

 In the lower jaw the incisors, canines, 1st and 4th post-canines had cut the gum. 



As compared with the Elephant Seal, the zygomatic arches were much flatter, and the 

 greatest width was towards the posterior end. The zygomatic and temporal fossae were 

 not so capacious relatively to the size of the skull, but the frontal region in Otaria was 

 much more constricted immediately behind the orbits. In the two adult male skulls the 

 distance from the anterior surface of the cranial box (the tubercular process not being 

 included) to the antorbital process was about twice as great as the orbital diameter from 

 the antorbital process to the orbital process of the malar. In the smaller adult from 

 the Chincha Islands the orbital diameter was three-fourths that of the entire distance, 

 and in the Maldonado skull two-thirds. In the young male from the Falkland Islands 

 the two diameters were almost equal. It follows, therefore, that whilst in the young 

 animal the back of the orbit is in close relation to the front of the cranial box, in the 

 adult male it is separated from it by a wide interval, which marks the position of the 

 temporal muscle and acquires its magnitude in relation to the use of that muscle in the 

 masticatory process. The zygomatic process of the temporal did not curve upwards so 

 abruptly as in the Elephant Seal, and did not reach the tip of the orbital process of the 

 malar, which was much more stunted than in the Elephant Seal. 



The nasal bones were relatively short and not ankylosed except in the Maldonado skull ; 



