Archive image from page 294 of Discovery reports (1934) Discovery reports discoveryreports08inst Year: 1934 THE SOUTHERN SEA LION 285 YEAR OF AGE 1st 2nd . 3rd . 4th . 5th Bthohover muscles now cover the whole of the sides and top of the cranium. The pterygoids and palatines project much farther below the level of the bony palate and the squamosals are fused to the supra-occipitals. The canines much exceed the outer incisors in length (Plates VIII, IX, X, figs. 6). The ADULT skull, that from an animal in its sixth year at the youngest, has an average length of 344-9 mm. (31 specimens); the p
Archive image from page 294 of Discovery reports (1934) Discovery reports discoveryreports08inst Year: 1934 THE SOUTHERN SEA LION 285 YEAR OF AGE 1st 2nd . 3rd . 4th . 5th Bthohover muscles now cover the whole of the sides and top of the cranium. The pterygoids and palatines project much farther below the level of the bony palate and the squamosals are fused to the supra-occipitals. The canines much exceed the outer incisors in length (Plates VIII, IX, X, figs. 6). The ADULT skull, that from an animal in its sixth year at the youngest, has an average length of 344-9 mm. (31 specimens); the proportion to body length is 14 per cent (9 specimens), the zygomatic width is 215-9 mm. and the hamulo-pre- maxillar length is 241-2 mm., the two last being 62-6 and 69-9 per cent of the total length of the skull. In this stage the nasals are almost quite flat, and in profile are in the same straight line as the median anterior prolongations of thefrontals, which are now below the level of the post-orbital processes. In profile the line of the nasals and the anterior parts of the frontals forms an angle of 160 degrees or less with the dorsum of the cranium proper, the point at which the change of direction takes place being situated approximately at Fig- 4- Male sea lions. Variations in proportions during growth. the level of the posterior end of the ' 'u' '8 as percentage of body length. jugal. The profile of the upper ' '''''°;P'''f'''''''g'P''''g°f'''''' ° r 1 1 11 . r • , -r: Zygomatic Width as percentage of skull length. surface or the skull as a whole is thus once more bent, instead of being straight as it was in the fifth year. This change of direction of the profile increases with age, being 150 degrees in the skull No. 335X of the National Collection; it tends to be obscured, however, by the development of the sagittal crest. Other osteological characters of the adult are these: the frontal and parietal segments are fused together, the alisphenoid is united to
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