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inches. The symphysial surface, contrasted with the molar teeth, seems 

 enormous ; its antero-posterior extent to the fractured end of the jaw is 

 six inches, its vertical diameter three inches ; its direction is obliquely 

 from below upwards and forwards, its upper or posterior margin nearly 

 straight, its lower or anterior one convex ; it stands out a very little way 

 from the vertical plane of the inner surface of the ramus. The thickest 

 part of the symphysis of the jaw does not exceed three inches ; this is at 

 its lower part, which is convex in every direction. The surface of the 

 bone seems to have been naturally roughened by minute vascular grooves 

 and ridges ; it has been crushed and cracked. The ridge, which doubtless 

 formed the anterior part of the base of the coronoid process, begins to stand 

 out below the socket of the third grinder ; the smooth abraded surface at 

 the back of the posterior talon of that tooth indicates the pressure against 

 a contiguous tooth in the portion of jaw which has been broken away. 



This symphysial portion of jaw differs in a striking degree from the 

 corresponding part in the known existing or extinct Pachyderms, which 

 have, like the Australian extinct Mammal, a single incisor tusk in each 

 ramus of the lower jaw. In the young Mastodon the tusk is situated in 

 a less deep, more suddenly contracted and more produced symphysis ; the 

 symphysis of the jaw in the Sumatran and incisive Rhinoceros is much 

 less deep and is broader in proportion ; the peculiar deflection of the 

 symphysis in the Dinotherium makes it differ still more strikingly from 

 the Diprotodon, in which the incisive tusks of the lower jaw extended 

 obliquely upwards. The sudden slope of the toothless margin of the jaw 

 anterior to the molares distinguishes the existing Proboscidians, which 

 have a smaller anchylosed symphysis and no lower tusks. 



In the proportion of the symphysial articulation to the molar teeth, I 

 know of no quadruped that so nearly resembles the present large Austra- 

 lian fossil as the Wombat ; but in this Marsupial that part of the ramus 

 of the jaw is broader in proportion to its depth : in these dimensions, 

 viz. the proportions of breadth to depth of the jaw supporting the anterior 

 molares, the Kangaroo more resembles the Diprotodon ; and the molars 

 of the Kangaroo in their double roots and double-ridged crowns are those 

 amongst the Marsupials which most nearly resemble the molars in the 



