ARCHAEOTHERIUM. 63 
Anteriorly, the crowns are embraced by a strong and deep basal cingulum or 
ridge, relatively more robust than in any of the allied genera. 
In the first true molar a strong basal ridge passes in a festooned manner from the 
apex of the postero-internal lobe posteriorly to the base of the corresponding ex- 
ternal lobe, and from this externally to the base of that in advance, but does not 
embrace it as in Entelodon magnum. 
In the second true molar, as in the corresponding tooth of Entelodon magnum, 
the apex of the postero-internal lobe is continuous with a thick basal ridge ascend- 
ing posteriorly from the base of the postero-external lobe; but no ridge exists ex- 
ternally upon the tooth as in the latter animal. 
The last of the true molar series has a quadrilateral oval crown, presenting as in 
the teeth described, an anterior row of lobes, bounded at base anteriorly by a similar 
but shorter and more tuberculated basal ridge. The posterior third of the triturating 
surface is composed of an assemblage of four low tubercles, which correspond to 
the posterior lobes and basal ridge of the two molars in advance. 
The posterior two premolars are not at all like those of Hyracotherium, but are 
constructed upon the same pattern as those of Choeropotamus, and are very much 
like those of Entelodon magnum. 
As in the latter, the last premolar has a quadrilateral crown with the inner side 
shortest and that anterior oblique. It is composed of a transverse pair of conical 
lobes, of which the internal is the smaller, and both are very much larger than the 
homologous constituents of the true molars. Posteriorly they are associated by a 
strong basal ridge, a portion of which exists also at the anterior part of the outer 
lobe, but no portion exists internally and externally as in Entelodon magnum. 
The crown of the penultimate premolar forms a single, large, laterally compressed 
conoidal lobe, resembling very much that of a corresponding carnivorous tooth. It 
is relatively greater antero-posteriorly, and is narrower than that of Choeropotamus, 
and is very much like that of Hntelodon magnum ; but, judging from Gervais’s sketch 
of this tooth of the latter, is more uniform in its transverse diameter. Externally 
it is convex, and in its direction downward curves slightly backward. Its anterior 
margin is convex, but posteriorly it presents a salient margin separating the external 
and internal faces. Posteriorly, the internal face towards the base of the crown is 
rugged, and anteriorly it presents a portion of a basal ridge, which forms a double 
festoon downward. 
_The enamel of the molar teeth of Archaeotheriwm is everywhere corrugated, but 
this appearance wears off as age advances. 
In the trituration to which the true molars are subjected, the enamel at the 
apices of the lobes is first worn through, and the exposed dentine afterwards extends 
across the latter in transverse tracts. 
The posterior two premolars, in the specimen upon which the species was origi- 
nally established, exhibit the result of considerable mastication. In the last pre- 
molar the posterior basal ridge is partially worn away, and the anterior portion of 
the same ridge and the division between the lobes are completely obliterated. The 
triturating surface in its present condition, presents a broad, transversely ellipsoidal 
