354 PALEONTOLOGY. 



the succeeding teeth, like the carnassials of Carnivora, are, like 

 the blades of shears, adapted to cut and divide soft substances, 

 such as flesh. As in Carnivora, also, these sectorial teeth are 

 succeeded by a few small tubercular ones. The jaw conforms 

 to this character of the dentition. It is short in proportion to 

 its depth, and consequently robust, sending up a broad and 

 high coronoid process (&), for the adequate grasp of a large 

 temporal muscle ; and the condyle (c) is placed below the 

 level of the grinding teeth — a character unknown in any 

 herbivorous or mixed-feeding Mammal ; it is pedunculate, as 

 in the predaceous marsupialia, whilst the lever of the coronoid 

 process is made the stronger by the condyle being carried 

 farther back from it than in any known carnivorous or herbi- 

 vorous animal. The angle of the jaw makes no projection 

 below the condyle, but is slightly bent inward, according to 

 the marsupial type. 



Sp. Plagiaulax minor, Fr. — In this species the first pre- 

 molar (fig. 120, p, i) is pre- 

 served ; the rest (p, 2, 3, and 4) 

 shew nearly the same shape and 

 proportions as in P. Becclesii. 

 The first molar (m, 1) has a 

 ^^ 120 broad depression on the grind- 



Plagiaulax minor (four times nat. size), ing Surface, Surrounded by 



Purbeck (after Lyell). tubercles, of which three are 



on the outer border ; the marginal tubercles of the second 

 molar (m s) are smaller and more numerous. 



In the general shape and proportions of the large premolar 

 (p, 4) and succeeding molars, Plagiaulax most resembles 

 Thylacoleo (fig. 173, p, m 1 and 2), — a much larger extinct 

 predaceous Marsupial from tertiary beds in Australia. But 

 the sectorial teeth in Plagiaulax are more deeply grooved ; 

 whence its name. The single compressed premolar of the 

 kangaroo-rat is also grooved ; but it is differently shaped, and 



