CHAP. IX.] 



TEETH : PINN1PEDIA. 



241 



329. P. vitulina : having a supernumerary tooth in each jaw on the 

 right side. This is a somewhat remarkable case. In both jaws the 

 extra tooth does not stand in series with the others but is placed 

 within the arcade (Fig. 59, + + ). That of the upper jaw is a curved 

 tooth with one large median cusp and a small cusp anterior to and 

 posterior to it, having somewhat the form of p z of the lower jaw. This 

 tooth stands within the arcade at a level between that of j^ and F J which 

 are pushed outward by it. The extra tooth of the lower jaw in shape 

 closely resembles that of the upper jaw, but is slightly larger, having 

 very much the size and shape of the lower right jja. In position this 

 extra tooth does not stand between p* and p 3 like the upper supernum- 

 erary, but is placed within the arcade and p* and p~ 4 which are some- 

 what separated by it. C. M., 903. [Judged by the ordinary rules of 

 dental homology, the two extra teeth are not homologous, for the 

 upper one is between p- and p 3 , while the lower one is between p and 

 yA But when the jaws are put together it appears that the two extra 

 teeth are opposite to each other almost exactly, the large cusp of the 

 lower one being in the bite scarcely at all posterior to the large cusp of 

 the upper. The tooth of the lower jaw is thus almost exactly the 

 image or reflexion of the tooth in the upper jaw.] 



Fig. 60. Phoca vitulina, No. 329; view of upper teeth from the surface, and 

 an imaginary profile of the upper and lower teeth of the right side seen from 

 within. 



'0. Otaria ursina : this skull in bad condition. The Catalogue 

 (1884) states that between p 2 and F J on both sides and between P^ and m^ 

 on both sides there was a small supernumerary tooth, in all, four extra 

 teeth in the upper jaw. The anterior supernumeraries are in place and 

 one rather smaller than p\ The posterior supernumeraries are lost, but 

 from the alveoli they must have been of fair size, though not so large 



B. 16 



