58 ON THE EXTINCT MAMMALIA OF 



molar of the upper jaw is more posterior and external in its relation with the con- 

 tiguous sectorial tooth. Their crowns generally are proportionately longer, narrower, 

 more pointed and more .trenchant than in the true cats. In the unworn condition 

 the acute borders are all distinctly but minutely crenulate. 



Siiperior molars. — The first upper premolar occupies the same relative position as 

 in Felis. In a young skull, in which all the molars have protruded but are unworn, 

 and the upper canines had but partially protruded, the first premolar, as represented 

 in figure 2, plate IV, has about the same relative size as in Felis. It has a laterally 

 compressed conoidal crown, longest in advance 6f the middle; and is inserted by a 

 pair of fangs. In the skull represented in figure 1 it had been shed, and the alveoli 

 have disappeared. In the older specimen (in which the upper sectorial molar has 

 its crown more than half worn away) represented in figure 5, on one side it had been 

 shed and the alveoli obliterated ; but on the other side it appears to have been a 

 single-fanged tooth, and the fang remains in its alveolus. 



The second upper premolar is smaller in relation with the succeeding tooth than 

 in Felis. Its crown is trilobed, and is of more uniform thickness at base than in the 

 latter. The anterior lobe is the smallest, and less distinct than the others. It is 

 represented in Felis by an extension forward of the base of the principal cusp. The 

 posterior lobe is broad, simple and trenchant, and not indented or sub-divided as in 

 the true cats. 



The upper sectorial molar, besides the proportionately longer and narrower crown 

 in relation with the breadth, exhibits other differences from the corresponding tooth 

 of Felis. The anterior sub-lobe, proportionately smaller than in the latter, possesses 

 a strong oflset or heel projecting from its base antero-externally. The median cusp 

 and the broad posterior trenchant lobe include between them externally, as in the 

 cats, a wide depressed surface, but this does not converge into a conspicuous fossa, as 

 in the latter. 



The tubercular molar is proportionately much larger than in the cats, and is 

 absolutely as large as that of the Lion. It is situated nearly transversely posterior to 

 the position of the sectorial molar, extending inwardly in the usual manner in the 

 cats. It is inserted by a pair of fangs, one internally to the other. The crown is 

 rather ellipsoidal transversely, and slightly curved backward. The outer half is the 

 thicker, and projects nearly on a level with the lower border of the back angle of the 

 sectorial molar. The inner half is abruptly impressed, or cut out in an obtusely 

 angular step or heel. A curved, linear, crenulated ridge crosses the crown near its 

 middle from before backward. The crown of the tubercular molar was worn away 

 at the fore part externally, in keeping sharp the point of the posterior trenchant 

 lobe of the inferior sectorial molar. 



