13 



also forty-two teeth, and is thirteen feet two inches long. I 

 subjoin a table of the proportions of these three under jaws 

 assumed to belong to the same species, that is, Catodon 

 Australis. 



According to Mr. Gray, who probably, with Beale, took 

 John Hunter as his authority for the assertion, not only the 

 number of teeth varies according to age, but the length of the 

 lower jaw appears to increase in front, so that in the older 

 specimens the symphysis is more, and in the younger ones 

 less than one -half of the entire length of the under jaw. In 

 our three Sydney under jaws there can be no doubt that the 

 disproportion between the length of the symphysis and half 

 length of the entire jaw goes on increasing according to the 

 size of the animal ; but all three have their symphysis longer 

 than half the length of the under jaw. It is also certain that 

 the inspection of the greatest "under jaw in the Sydney 

 Museum, may induce one to think it possible that, as Mr. 

 Gray says, the symphysis increases with age in a greater 

 proportion than the whole length of the lower jaw. By the 

 way, I may remark, that this largest specimen also appears to 

 exhibit more than forty-two dentary alveoles or sockets. We 

 thus have John Hunter's position illustrated, that " the exact 



