AECHABOTHERIUM. g3 



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 Glioeropotamus, 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 Ohoeropotamus, 

 and is very much like that of Entelodon 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 Archaeotherium 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 



