325 
of the wild Boar, and Animal incognitum. 
are afterwards formed, being scarcely more than half their size : 
they have three transverse projecting ridges, completely en- 
crusted with enamel, as well as every other part of the masti- 
cating surface. 
Two of these grinders, and probably more, are present on 
each side of the jaw at the same time. As the animal increases 
in size, and the jaw extends itself, a larger kind of grinder is 
formed in the posterior part of the jaw, exactly similar to what 
happens in the elephant ; and, as this large tooth, which has five 
projecting transverse ridges on the masticating surface, becomes 
completely formed, it comes forward, and occupies the principal 
seat in the jaw, and the others drop out. 
When the smaller grinders are examined, the greater num- 
ber of them have their fangs all bent in one direction, in con- 
sequence of the bodies of the teeth having been pushed for- 
ward, by the large posterior tooth coming into their place, 
as was observed in the temporary grinders of the young Sus 
Ethiopicus. 
This process is well illustrated by two specimens, which show 
the teeth in the two stages of growth, and which are represented 
in the annexed figures. 
The first is a lower jaw preserved in the Hunterian Museum* 
in which the two small grinders are in their sockets ; and the 
cavity for the formation of the large grinder has, upon its 
sides, the impression of the different parts of the body of the 
tooth. 
The second is a lower jaw in the British Museum, in which 
the large grinder is completely formed, and occupies the prin- 
cipal part of the jaw, at the anterior part of which are the 
