SI" AI .S 



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Remarks : — As in Ommatophoca the development of the sagittal crest is extremely 

 slight and the lambdoid crest is even weaker than in that genus. So too the nearest approach 

 to a crest is be found along the junction of the parietals and frontals near the middle Une. 



Both the basilar and sphenoidal sutures close completely before the animal becomes very 

 old, in contradiction to Ommatophoca and Ogmorhinus in which the sphenoidal suture seems to 

 remain open throughout life. 



As regards the sexes, those with the largest canines are most probably maies, and those 

 with the smallest females, but there are many spécimens the sex of which, if unlabelled, it would 

 be very hard to ascertain. 



The extraordinary cheek-teeth, although apparently so liable to suffer from wear and tear, 

 seem to préserve their appearance unworn in a very remarkable manner, wearing away in 

 fact at a far less rapid rate than the more massive canines and incisors, and for the most part 

 only at the anterior portion of the jaw and on the anterior surface of each tooth. 



Distinguishing Characteristics : — (a) The skull although not possessing the enormous 

 dimensions of that of Ogmorhinus may be at once distinguished at ail âges by the peculiar grinding 

 teeth, which are both large and remarkable for the complicated arrangement of cusps in which 

 they terminate superiorly. As in Ogmorhinus there is a principal central cusp, but this is suppor- 

 ted, not by two others, one on each side of it, but by one quite small cusp in front and by from 

 one to three behind. The central cusp is far larger than the remainder and its apex, which is 

 usually bulbous, points backwards. In addition to thèse dental characters, this species differs 

 from the somewhat similarly sized Leptonychotes in its longer palate and longer, broader anterior 

 portion of the skull, as well as in the quite differently shaped lower jaw. (See under Leptonychotes). 



