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codile, observes, that in the fossil jaw-bones of St. Peter’s Mountain, a 
small secondary tooth is formed, with its enamel and solid root, within 
the bony substance of the primordial tooth itself. These secondary 
teeth, by continuing to grow, seem to make, by degrees, sufficient 
cavities in the bony roots of the primary teeth ; but what becomes of 
them at last, and how they are shed, he adds, I am not able to guess*. 
From the existence of a hollow in the primary teeth of the fossil 
animal, and from the growth of the secondary tooth in this hollow, 
M. Fanjas is led to exclaim : “ It is difficult to conceive how this 
illustrious philosopher could permit so striking a character to escape 
him ; and, after witnessing this circumstance (the secondary tooth 
being formed near the centre of the bony support of the primary tooth), 
how he could conceive these teeth to belong to a cetaceous animalf 
The approximation of the secondary towards the centre of the primary 
tooth appears, however, in this animal, to have been merely an acci- 
dental occurrence. Nor does it appear that the mode of dentition at 
all coincided with that which is known to take place in the crocodile. 
On this subject M. Cuvier observes, that in the crocodile the tooth 
is always hollow ; that it is fixed in, but never attached to, the bone 
of the jaw ; and that the secondary tooth forms in the same socket, 
and frequently grows into the hollow of the primary tooth, thus 
shivering it, and occasioning it to be shed. 
The fossil animal of Maestricht, he remarks, on the contrary, like 
other animals, appears to have had its teeth hollow only whilst they 
were growing, they afterwards filling up, and becoming solid and fixed 
in the jaw by a fibrous and osseous substance, materially differing 
from the real substance of the teeth, although closely united with it. 
The secondary tooth, too, is here formed in a particular socket, which 
is formed at the same time with this tooth, which passes out, some- 
times at the side, and sometimes through the osseous substance which 
supports the primary tooth. In the end, it detaches this substance 
* Philos. Trans, for 1786, p. 178. f Hist. Nat. de la Mont, de St. Pierre, p. 240. 
