12 
DESCRIPTIONS OF INFERIOR MAXILLARY BONES 
exterior point rises two inches and three-tenths from the root and the 
inner one three inches and three-tenths, making a difference in the 
former of half an inch, and in the latter of one inch and one-tenth. 
The chin in this specimen contains about one half of the alveole for 
the exserted tusk (fig. 2, z). This alveole is rather more than two 
inches in diameter; its direction is outwards and downwards, less 
downwards however than in the preceding species; indeed there is a 
distinct difference in the position of these sockets in the two specimens. 
The base of the socket is smooth and flat, and its position somewhat 
oblique, so that it is rather deeper towards the exterior, than towards 
the interior; it is perforated by two small foramina for the nutrient 
arteries, and the nerves of the tusk. 
It is to be lamented that little positive can be ascertained, as to the 
localities in which the bones belonging to the Society, and which we 
have just described, were found, their position in the soil, &c. All that 
can be collected is, the probability, that they are from the Big-bone lick, 
and that they are those presented by our late president Thomas Jefferson, 
Esq., and which are noticed in the communication of Professor Wistar, 
in Vol. I. N. S., p. 376, of the Transactions. 
Dentition of the Mastodon. 
The specimens we have just described furnish some interesting in¬ 
formation relative to the dentition of the Mastodon, which we shall now 
proceed to lay before the Society. The form, and differences, succession 
and number of the teeth are all subjects of great interest; and in describ¬ 
ing them we shall follow Cuvier, adding such additional information as 
our investigations have brought to light. 
The crown of the teeth more or less approaches the rectangular form, 
slightly inclined however to rhomboidal, and rather narrower anteriorly 
than posteriorly. It consists of two substances, the interior osseous, the 
exterior enamel. The crown is divided by deep furrows into a num¬ 
ber of ridges or denticules, and these denticules are subdivided by one 
or more superficial and narrow processes or tubercles. The outer 
face of the crown rises nearly perpendicularly, the inner face rises ob¬ 
liquely inwards. In the lower jaw, the outer point is higher than the 
