MaJiimalia. 41 



tion. This cannot, however, be regarded as having been very suc- 

 cessful. It seems certain that those specimens which possess the 

 largest canine teeth are males, while those with the smallest are 

 females. But between the two extremes there are so many indi- 

 viduals in which these characters are intermediate that my deter- 

 minations can only be regarded as quite hypothetical. As far as 

 the evidence presented by the skull goes, there is no very marked 

 sexual difference. The differences of size would, however, I suspect, 

 arrange themselves more definitely about a mean, were it possible 

 to collate the specimens exactly by their sexes. 



Age. — Here again, except in the case of the specimens brought 

 home by the ' Belgica,' the remarks in the first column of my " Taljle " 

 must be regarded as purely hypothetical, although certainly resting 

 upon a securer foundation than in the case of sex. Both the basilar 

 and sphenoidal sutures close completely before the animal becomes 

 very old, in contradiction to what occurs in the case of Ovimatophoca 

 and Ogmorhinus, in which the sphenoidal suture seems to remain 

 open throughout life. As in Ommatophoca, the development of the 

 sagittal crest is very slightly marked, and the lambdoid crest is 

 even weaker than in that species. Similarly the nearest approach to 

 !:he formation of the former crest is to be found along the parieto- 

 frontal junction, near the middle line. 



The extraordinary cheek-teeth, although apparently so liable to 

 suffer from wear and tear, yet seem to preserve their form in a very 

 remarkable manner. They wear away, in fact, at a far less rapid 

 rate than do the massive canines and incisors. Such damacje as 

 makes its appearance is for the most part confined to the anterior 

 teeth and to the anterior portions of these. In contradistinction to 

 the cheek-teeth, the canines and incisors may be broken and cut 

 as if by use in fighting. 



The skeleton has been described in detail by Sir Kichard Owen in 

 the catalogue of the Osteological Museum of the Pioyal College of 

 Surgeons of London (p. 642), and also in the ' Annals and Magazine 

 of Natural History ' for 1843 (p. 331). 



(See Table III, pp. 42-4.5.) 



