THE SOUTHERN SEA LION 



133 



Summary of observations on age groups of the female skull 

 The measurements given in the following paragraphs are averages. Since there is 

 invariably an increase in size it is not remarked on ; the figures are given in Table IV. 

 Fourth year. Fourteen winter specimens, total length 228-4 mm., 15-5 per cent of 

 the body length ; zygomatic width 121-3 mm., hamulo-premaxillar length 148-0 mm., 

 53-1 and 64-8 per cent of the skull length. The rounded outline is still somewhat remini- 

 scent of the immature skull and the facial region is less conspicuous than in later stages. 

 The vertical part of the palatine is still rather narrow and a short length of the lambdoidal 

 suture about the level of the parieto-mastoid suture is unfused. The canines are usually 

 small and the transverse groove in the edge of the incisors is still deep in most specimens, 

 or if worn is easily seen (see also 1934, p. 289). 



Table IV 



Average measurements and proportions of annual age groups (Females) 



Fifth year. Twenty-two winter specimens, total length 237-8 mm., 14-8 per cent 

 of the body length ; zygomatic width 128-3 mm., hamulo-premaxillar length 158-3 mm., 

 54-0 and 66-6 per cent of the skull length. The skull shows a distinct approach to the 

 adult character. The facial part has a relative increase in importance, the temporal lines 

 almost meet anteriorly, and indications of the development of bony crests for the attach- 

 ment of the jaw muscles may appear. The palate is more elongated and the vertical part 

 of the palatine is relatively deeper and better ossified than in the fourth year. The 

 hamular processes are more oblique and in their increased length approach the adult 

 condition. There is usually still visible a vestige of the lambdoidal suture at the level 

 of the parieto-mastoid suture. The upper incisors frequently show signs of wear, but 

 not to such an extent as to obliterate the transverse grooves. 



Sixth year. Eighteen winter specimens, total length 248-5 mm., 14-6 per cent of 

 the body length; zygomatic width 133-4 mm., hamulo-premaxillar length 166-9 mm, 

 53-7 and 67-2 per cent of the skull length. The principal alteration appears in the form 

 of a forward and usually slightly downward growth of the premaxilla and the canine part 



