350 $Supernumerary Tooth in Mastodon giganteus. 
bone, which seems to have been broken from the extremity of 
this fang. This tooth is slightly penetrated by oxyd of iron, 
increasing its weight. It measures from before backwards over 
the centre of the grinding surface four inches; transverse width 
anteriorly three inches, posteriorly three and a half inches; inner 
edge antero-posteriorly four and a half inches; outer edge an- 
tero-posteriorly three and a half inches. The basal cingulum is 
more prominent on the outer than on the inner side, and measures 
in circumference thirteen inches. ‘This tooth, it appears, is fully 
characterised as the fifth tooth in the lower jaw of M. giganteus. 
The tooth behind this is an ultimate molar of the right side of 
the lower jaw. It is not removable from its socket, like the tooth 
last described, though not entirely fixed. Its crown is well worn 
though not so much as in the preceding tooth; it is divided into 
four ridges, has of course three transverse fissures and eight cusps, 
two cusps on each ridge. The cusps are all worn, the anterior 
ones very much, the posterior slightly. The longitudinal groove 
separates the cusps of the ridges from each other. There are no 
papilla. The worn surface is oblong in the transverse direction, 
and not rounded like the Mastodon Andium, nor lozenge-shaped 
as in the M. longirostris. The ridge of enamel surrounding the 
cusps is an eighth of an inch in diameter, rather thicker than in 
these Mastodons usually ; the cingulum is prominent on the outer 
edge, and flattened on the inner edge of the tooth; it measures 
eighteen inches in circumference. The anterior extremity of the 
away. ‘The posterior extremity is composed by a talon with a 
a 
checked its development. 
The two teeth already described having all the characters of 
the fifth and sixth teeth of the Mastodon giganteus, the tooth 
behind the sixth is a seventh, and is the only instance of the kind 
I have ever seen or heard of. This tooth is situated behind the 
sixth, and nearly in a line with it, but projects outwards from one 
to two inches more than the other, while its inner face is sur- 
| by that of the sixth tooth three quarters of an inch. The 
anterior face is in contact with the posterior face of the sixth 
tooth to a certain extent, though not exactly ; there being a slight 
deviation as mentioned in the position of the seventh tooth, the 
two surfaces in question do not correspond. The posterior face 
of the seventh tooth is imbedded in the bone, so that it cannot 
be seen, nor described ; but the buried part of it seems to have the 
teat of ain, oT be, oxterank foes oh DREIAR epeceapons witht 
he root coronoid process. Its superior face presents 
aree ridges crossed by a longitt 
