PLAGIAULAX 319 



as in Phascolothermm ; and the condyle, besides being on a 

 lower level, is divided by a less deep notch from the coronoid 

 process. This process is larger in proportion to the entire jaw ; 

 approaches more nearly to the quadrate or rhomboid form, the 

 upper border being less curved ; it affords a more extensive 

 surface of attachment to the principal biting muscles than in 

 most predatory extinct or recent quadrupeds. This character, 

 with the depth and strength of the jaw, suggested the specific 

 name. From the shape of the exposed part of the ramus, we 

 may conclude that the part answering to the angle is bent in- 

 wards, and that Triconodon was a genus of the marsupial order. 

 The specimen was discovered by Mr. Beccles in the same " dirt- 

 bed" at Purbeck as that in which Spalacothcrium was found. 



Genus Plagiaulax,* Fr. — The most remarkable of Mr. 

 Beccles' discoveries in the above formation are the mainmalian 

 jaws indicative of the genus above named, of which two species 

 have been determined by Dr. Falconer. 



Sp. Plagiaulax Becclesii, Fr. — Two specimens exemplified 

 the shape and pro- 

 portions of the entire 

 jaw of this species 

 (fig. 92). The fore- « 

 most tooth (i) is a .• 

 very large one, \ 

 shaped like a canine, 



but implanted by a , g " 92 ' 



. Plagiaulax Becclesii (twice nat. size), Purbeck. 



thick root m the 



fore part of the jaw, like the large lower incisor of a shrew or 



wombat. The three anterior teeth in place have compressed 



trenchant crowns, and rapidly augment in size from the first 



(2) to the third (4). They are followed by sockets of two 



much smaller teeth, shown in other specimens to have sub- 



* An abbreviation for Plagiaulacodon, from wAdytos, oblique, and auAo|, 

 groove; having reference to the diagonal grooving of the premolar teeth. 



