38 



has the same form and construction, with the addition of a third but smaller 

 lobe. 



In the unworn molars the principal constituent lobes present acute cres- 

 centoid summits embracing a concavity which opens to its bottom by an 

 angular notch on the inner side of the crown. The contiguous arms of the 

 crescentoid summits conjoin in a strong conical eminence situated just in 

 advance of the middle of* the crown internally. The point of this eminence 

 is simple or undivided ; in Auchitherium it is deeply indented and appears to 

 be composed of a connate pair of eminences. 



The fore part of the summit of the anterior lobe in Palaeosyops curves 

 downward and inward, and ends in a slight prominence at the anterior inner 

 corner of the crown. The hind part of the summit of the posterior lobe ends 

 in a prominence like that in advance, but smaller, and situated at the postero- 

 internal corner of the crown. 



Externally the lobes of the crown are angularly convex, and include deep 

 angular recesses sloping outwardly and downward, and bounded by festooned 

 elements of a basal ridge. The inner surface of the crown is nearly vertical, 

 smooth, and without a basal ridge. The latter is especially well developed 

 at the fore and back part of the crown, except in the last molar, in which the 

 additional lobe takes its place. This lobe is a much reduced likeness of those 

 in advance, with the arms of its crescentoid summit contracted and conjoined 

 with the posterior conical eminence of the crown internally. 



The molars undergo a rapid reduction forward, and they are inserted by 

 two fangs. The crown of the last premolar is a reduced representative of 

 that of the succeeding molar, with the posterior lobe proportionately, in 

 comparison with the anterior lobe, less well developed. In the crown of the 

 third premolar there has been a further proportionate reduction in the back 

 lobe, but the anterior remains nearly the same, except that it appears more 

 robust from its connation with the homologue of the anterior of the inner 

 conical eminences of the teeth behind. 



In Palaeotherium and Auchitherium the corresponding premolars with those 

 described repeat the form of those of the molars, and in tins respect greatly 

 differ from Palaeosyops. The inferior premolars of Titanotherium in a perfect 

 condition are not sufficiently well known to institute a comparison with those 

 of Palaeosyops. 



The lower molars of Palaeosyops in wearing would assume the same 



