320 PALEONTOLOGY 



tuberculate crowns resembling those of Microlestes. The large 

 front tooth of Plagiaulax is formed to pierce, retain, and kill ; 

 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 (b), 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 ; 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 

 herbivorous animal. The angle of the jaw makes no projec- 

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

 to the marsupial type. 



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



(fig. 93, p, i) is preserved ; the 

 rest (p, 2, 3, and 4) show nearly 

 the same shape and propor- 

 tions as in P. Becclcsii. The 

 first molar (m, 1) has a broad 

 "jrjo. 93 depression on the grinding 



Plagiaulax minor (four times nat. size), surface, SUlTOimded by tuber- 

 Purbeck (after Lyell). ^ Qf wMch ^^ m Qn ^ 



outer border ; the marginal tubercles of the second smaller 

 tooth are smaller and more numerous. 



In the general shape and proportions of the large premolar 

 (^>, 4) and succeeding molars, Plagiaulax most resembles 

 Thylacoleo (fig. 141, 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 



