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



jaw. The angle was marked by a ridge-like tubercle wdiich projected backwards. A 

 strong, quadrangular, inflected subcondyloid process sprang from the posterior border of 

 the ascending ramus ; it was separated by a notch from the ridge-like angle, and by a 

 still deeper notch from the neck and condyle. The coronoid was broad, thin, and formed 

 an obtuse angle. The body was massive, with its lower border everted, and closely 

 corresponded in its characters to the description given by Dr. Murie. The mandible in 

 the young skull showed on a smaller scale the same character as the adult. 



The differences between the larger and smaller adult crania, in addition to that of 

 size, may be summarised as follows : — In the smaller skulls the occipital and sagittal 

 crests were feeble ; no parietal tubercle ; the antorbital processes much smaller; the 

 interfrontal diameter relatively larger ; the front of the premaxilla was both absolutely 

 and relatively less deep, and its nasal tubercle was scarcely marked ; the breadth of the 

 palate was greater behind the molars ; the tympanic bulla was prolonged downwards 

 into a sharp ridge instead of a thick, truncated process ; the length of the brain-cavity 

 in the smaller crania, especially the Maldonado specimen, was, in proportion to that of 

 the entire skull, greater than in the larger specimens ; and the antero-posterior 

 diameter of the orbit bore a larger proportion to the distance between the front of the 

 cranial box and the antorbital process. These differences cannot be ascribed to age, 

 for the smaller skulls were as perfectly ossified as the larger crania. As nothing 

 is known of the sex of the animals from which the smaller crania were derived, it 

 cannot absolutely be stated that the differences were sexual only, though without doubt, 

 for the most part, they were such as are mainly occasioned by a more vigorous ossification 

 in the one skull than in the other, as we are in the habit of recognising in male crania 

 when compared with female. That important sexual differences do exist in the crania 

 of the Sea Lions has already been pointed out by Sir Richard Owen, 1 Mr. J. A. Allen, 2 

 and Dr. J. Murie, 3 and both Drs. Gray 4 and Murie have dwelt on the changes in form 

 which the skull undergoes in passing from the young stage to that of adult life and old 

 age, and the specimens now before me show that the characters of the two smaller adults 

 in many respects approximated to those of the young male Falkland Island cranium. 



The opinion of zoologists has greatly fluctuated regarding the number of species 

 which should be referred to the genus Otaria, even when that genus is restricted 

 according to the definition given on p. 29. A perusal of the numerous papers on the 

 Eared Seals by the late Dr. J. E. Gray will show how frequently he changed his views 

 on this subject. In a similar manner the late Professor Peters of Berlin from time to 

 time either added to or subtracted from the number of species. It is unnecessary to give 

 a resume of their various changes of opinion, as this has already been done by Mr. J. A. 



1 Catalogue, Royal College of Surgeons. 



2 Bull. Mus. Corwp. Zool, Cambridge, U.S., vol. ii. 1870-1871 ; and History of North American Pinnipeds, 1880. 



3 Proc. Zool. Soc. Lond., 1869 ; Trans. Zool. Soc. Lond., vol. viii. 



4 Proc. Zool. Soc. Lond., 1859 ; and Catalogue of Seals and Whales. 



