26 On the Skulls of Sea-bears and Sea-lions. 



antarctieus and Zalophus Gilliespii is elongate, coming far 

 forward, and acute in front, and becomes shorter, narrower, 

 and rounded in front in the full-grown animals. 



It is to be observed that the two forms of the opening to the 

 palate have been observed in the two species of the genus 

 Euotaria. 



All these variations have been considered characteristic 

 of species when only one skull has been examined ; but the 

 accession of a larger series of skulls shows how these parts 

 vary during growth, and perhaps from accidental circum- 

 stances, and shows the necessity of examining a series of 

 specimens of each species. 



The British Museum contains some skulls that exhibit the 

 differences that exist in the skulls of the two sexes of these 

 animals. The skulls of the males, in common with the males 

 of the Seals, are known by the larger size of the canines ; and 

 their large size renders a broader muzzle necessary to contain 

 them. Probably other characters would be observed if we 

 had a larger series, and knew the sexes to which they belonged. 

 For example, the British Museum possesses several skulls 

 of the Phocarctos Hooheri from the Southern seas. The one 

 figured in the ' Zoology of the Erebus and Terror ' appears, 

 on account of the small size of the canines, to be that of a full- 

 grown female ; and there are two skulls from the same expe- 

 dition which appear from the size of their canines, which are 

 being gradually developed, to be skulls of full-sized but young 

 males. The two males, 336 b and 336 e, have larger crowns 

 to the grinders, and the lower jaw of each is strong and broad ; 

 whereas the skull of the older female, 336 a, which has the 

 canine teeth and outer upper cutting-teeth perfectly developed, 

 has these teeth much slenderer than in the skulls of what I 

 consider to be males ; the grinders have smaller crowns, 

 which are placed rather further apart from one another than in 

 the males, but occupy the same length of the margin of the 

 jaw. These skulls also present a difference in the size of the 

 occipital condyles. The occipital condyles of the two young- 

 males are large, 2 T V in. wide, while the occipital condyle of 

 the adult female is much smaller, only 2^- in. wide in the 

 widest part ; and they are of rather a different shape in the 

 skulls of the two sexes. 



Since this paper was written, I have received the third part 

 of the ' Proceedings of the Zoological Society ' for 1873, which 

 contains a paper by Mr. J. W. Clark, the keeper of the Anato- 

 mical Museum of the University of Cambridge, "On the Eared 

 Seals of the Auckland Islands," from which it appears that 



