Mr. Koch on the Genus Tetracaulodon. 227 
and Mastodon. He says that in his collection there is a fragment 
of a lower jaw of this species with a tusk which shows very distinctly 
the difference of the lower tusks in the T. Godmanii from those of 
the T. Kochii, the character consisting in the root of the tusk being 
pointed ; and he states that he has not been able to discover the 
place occupied by the dental nerve. 
2. Tetracaulodon Kochii.—Of this ‘ species” the author pos- 
sesses three lower jaws of adults, and one of an extremely young 
animal ; also two upper tusks belonging to two different individuals, 
and two which belonged to one Tetracaulodon. Mr. Koch states 
that he found the roof of a mouth of this species perfect, with its six 
molar teeth and the tusks in their “ maxillary bones” resting on the 
lower jaw which retained a tusk in the alveolus, but that the veins 
of iron intersecting the deposit prevented him from extracting this 
valuable specimen entire, but that he secured the upper tusks and 
grinders, and the lower jaw with the tusk in its alveolus. It does 
not require a close examination, the author says, to perceive that 
the animal to which these remains belonged was neither male, fe- 
male, nor young Mastodon, or Missourium, the whole inner and 
outer conformation of the upper tusks showing that they were cal- 
culated to be used in harmony with the lower tusk in grubbing 
and rooting. Hence the author infers that the Tetracaulodon lived 
principally on roots, whereas the Mastodon, he says, consumed the 
large upper herbage. The superior tusks of this specimen measure 
only 19 inches in length, one-third having been ‘concealed in the 
skull,” and their greatest circumference is 94 inches. They possess 
the peculiarity of being larger at the apex than the base, the 
former also exhibiting indisputable marks of having been much 
used during the life of the animal. They were slightly curved up- 
wards. The enamel on the root is very thin, but it increases rapidly 
towards the extremity, where it is extremely thick. “ The bulb for 
the dental nerve” is stated to be small and to terminate suddenly in 
a point. 
With reference to the tusks of the lower jaw, Mr. Koch agrees 
to the view that the young animal possessed two, and the adult 
only one, situated on the right side. It was, he says, slightly 
curved downwards and then upwards, and in both old and young 
animals possessed the peculiarity of being equal in circumference 
at both extremities. The bulb for the nerve which nourished the 
tusk resembles minutely that of the upper tusks, both in adult and 
immature animals; and Mr. Koch is of opinion that this peculiarity 
of the lower tusks gives rise to “a suspicion of not merely a dif- 
ferent variety of the Tetracaulodon, but even of a new genus.” 
3. Tetracaulodon Tapiroides.—This specific distinction Mr. Koch 
has founded on the first grinder resembling that of the Tapir. He 
possesses the greater part of a skull and its two tusks, which were 
in their proper position when he found the specimen. ‘The tusks 
are described as perfectly straight, but bent downwards like those 
of the Morse, to which, the author says, they bear a strong resem- 
blance ; and, from their worn condition, he believes that the animal 
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