288 



DISCOVERY REPORTS 



width IOI-6 mm., 54-5 per cent of the skull length; hamulo-premaxillar length 114 mm. 

 61 -2 of the total length. There 

 is very little difference from the 

 male skull of the same age 



15T 



Z70 



except for smaller size and more 

 insignificant development of the 

 pre-orbital region. The temporal 

 line is about level with the post- 

 orbital processes, and the whole 

 cranium is smooth and rounded. All 

 the permanent teeth are present, 

 but the permanent canines scarcely 

 show above the gum and, as in the 

 male, milk canines may be present. 

 All the sutures may be traced, but 

 the components of the occipital 

 segment have begun to fuse. The 

 suture between the basi-occipital 

 and the basisphenoid is open (Plates XI, XII, XIII, figs. i). 



250- 



230 



2ID- 



190 



End 



YEAR OF AGE 

 3rd 4th , 



-h 



5th 6thorOve:r 



BODY LENGTH [CM] 



SKULL LENGTH [MM] 



HAMULO-PREMAXILLAR LENGTH[mm] 



ZYGOMATIC WIDTH [MM] 



170 



-150 



130 



110 



Fig- 5- 



Female sea lions. Increase in measurements 

 during growth. 



SECOND YEAR. Total length 201 mm 

 width 1 10 mm., 547 per cent of the 

 length ; and hamulo-premaxillar 

 length 125-3 nirn-j 62-3 per cent. 

 The cranium is slightly flattened 

 and the facial region slightly better 

 developed in proportion to the 

 skull as a whole, while the temporal 

 line has moved up towards the 

 middle line as the jaw muscles 

 have developed. On the whole the 

 teeth have increased in size and 

 the permanent canines are now 

 present and the longest teeth in 

 the jaws. There is increased fusion 

 of the occipital region but all the 

 other sutures are patent (Plates XI, 

 XII, XIII, figs. 2). 



THIRD YEAR. Total length 

 212-5 mm., 17-0 per cent of the 

 body length; zygomatic width 



17-0 per cent of the body length; zygomatic 



YEAR OF AGE 

 3rd . 4th 



Stth 6th or over 



Fig. 6. Female sea lions. Variation in proportions 

 during growth. 



SP: Skull length as percentage of body length. 



HP: Hamulo-premaxillar length as percentage of skull length. 



ZP: Zygomatic width as percentage of skull length. 



113-5 mm., 53'4 P^'' ^^"^ °f ^^^^ ^°^^^ length; hamulo-premaxillar length 132-2 mm., 

 or 62-2 per cent of the length. The flattening of the cranium is more pronounced. 



